commissioning switches, medium & high voltage

Note: The source of the technical material in this volume is the ProfessionalEngineering Development Program (PEDP) of Engineering Services.

Warning: The material contained in this document was developed for SaudiAramco and is intended for the exclusive use of Saudi Aramcos employees.Any material contained in this document which is not already in the publicdomain may not be copied, reproduced, sold, given, or disclosed to thirdparties, or otherwise used in whole, or in part, without the written permissionof the Vice President, Engineering Services, Saudi Aramco.

Chapter : Electrical For additional information on this subject, contactFile Reference: EEX30211 W.A. Roussel on 874-6160

Engineering EncyclopediaSaudi Aramco DeskTop Standards

Commissioning Medium/High Voltage Switches

Engineering Encyclopedia Electrical


Saudi Aramco DeskTop Standards

Content Page

INTRODUCTION................................................................................................................1

SAUDI ARAMCO REQUIREMENTS.................................................................................2

Indoor-Type..............................................................................................................4

Outdoor-Type...........................................................................................................8

EVALUATING MEDIUM/HIGH VOLTAGE SWITCHES UPON RECEIPT....................11

Visual Inspection......................................................................................................11

Verification Against Specifications...........................................................................11

Ratings and Nameplate Data.........................................................................12

EVALUATING MEDIUM/HIGH VOLTAGE SWITCH INSTALLATION ANDTESTING............................................................................................................................14

Visual Inspection......................................................................................................15

Alignment.....................................................................................................15

Contacts.......................................................................................................16

Mechanism/Linkage......................................................................................16

Three-Phase Contact Blades Make and Break Together................................17

Physical Damage...........................................................................................17

Lubrication...................................................................................................18

Cleanliness....................................................................................................18

Suitability.....................................................................................................19

Mechanical Inspections and Tests.............................................................................19

Open/Close Operation...................................................................................20

Arcing Horns Function..................................................................................20

Bolt Torque..................................................................................................21

Contact Wipe................................................................................................22

Mechanical Locking of Contact Blades.........................................................22

Key Interlock System Operation...................................................................23

Electrical Tests.........................................................................................................25

Contact Resistance........................................................................................25

Insulation Resistance.....................................................................................26




Oil Dielectric................................................................................................26

High Potential...............................................................................................27

SYSTEM PRE-OPERATIONAL CHECK-OUT.................................................................29

Point-to-Point Wiring Check....................................................................................29

Subsystem Check-Out..............................................................................................29

Interlocks.................................................................................................................29

SYSTEM OPERATIONAL TESTING................................................................................30

Source Feed Compatibility........................................................................................30

Complete System Functional Test.............................................................................30

WORK AID 1: REFERENCES FOR EVALUATING MEDIUM/HIGHVOLTAGE SWITCHES UPON RECEIPT...............................................32

Medium and High Voltage Load Interrupting Switch applications Checklist..............38

WORK AID 2: REFERENCES FOR EVALUATING MOTOR VARIABLESPEED DRIVE INSTALLATION AND TESTING..................................39

Information, Formulas, and Tables for Use in Evaluating theResults of Insulation Resistance (Megger) Tests.......................................................42

AC or DC Hi Pot Tests............................................................................................43

Information, Formulas, and Tables for Use in Evaluating theResults of Hi-Pot Tests.............................................................................................43

GLOSSARY........................................................................................................................48




Table of Figures Page

Figure 1: Disconnect Switch Use on Example Feeder Bus (Type CA SwitchgearArrangement).........................................................................................3

Figure 2: S&C Model PMH-9 Pad-mounted Switch.................................................5

Figure 3: Three-Pole, Vertical, Motor-Operated, Loadbreak Disconnect Switch.......6

Figure 4: Cut-Away View of a Typical Arc Extinguishing Chamber..........................7

Figure 5: Typical, Single-Pole, Medium-Voltage Disconnect Switch.........................9

Figure 6: Close-Up View of a Disconnect Switch Contact Assembly........................10

Figure 7: Example Application of Disconnect Switch Key Interlocks.......................24

Figure 10: Saudi Aramco Requirements forPad-Mounted Switchgearwith Load-Interrupting Switches............................................................32

Figure 11: Voltages and Insulation Levels for Load Interrupting Switches(From ANSI C37.72 - 1987)..................................................................33

Figure 12: Load, Cable Charging, and Interrupting Current Ratings(From ANSI C37.72 - 1987)..................................................................33

Figure 13: Guidelines for the Application and Selection of LoadInterrupting Switches.............................................................................34

Figure 14: Construction Requirements for Medium and High VoltageSwitch Types.........................................................................................35

Figure 14: Construction Requirements for Medium and High VoltageSwitch Types (Contd)...........................................................................36

Figure 15: Load Interrupting Switch Preferred Ratings (From C37.32-1990)...........37

Figure 16: Saudi Aramco Pre-Commissioning form, P-001, Switches;High and Medium Voltage Air, Oil, and SF-6........................................40

Figure 16: Saudi Aramco Pre-Commissioning form, P-001, Switches;High and Medium Voltage Air, Oil, and SF-6 (Cont'd)...........................41

Figure 17: Recommended Megger Test Voltages.....................................................42

Figure 18: Bolt Torque Values for Bus Connections................................................42

Figure 19: Table of Hi Pot Test Values....................................................................43

Figure 20: Example of Hi-Pot Testing (Good and Bad Insulation)...........................44

Figure 21: GI 2.710 Excerpt....................................................................................46

Figure 21: GI 2.710 Excerpt (Cont'd)......................................................................47



Saudi Aramco DeskTop Standards 1

INTRODUCTION

Large process and process support equipment in industrial facilities requires electric power tofunction. The electric power that is required to run equipment is passed through generation,transmission, and distribution systems that route the electric power to the correct equipment atthe proper voltage levels. Large, complicated, and costly switchgear, transformers, and circuitbreakers provide electric power control, fault isolation, and protection capabilities. Because ofthe size and complexity of power distribution systems, it is not economically feasible to useswitchgear and circuit breakers for every switching or isolation application. Additionally, someswitching applications do not require the capabilities and features that switchgear and circuitbreakers provide. Medium and high voltage switches provide an inexpensive alternative toswitchgear and circuit breakers.

The selection of the type and size of the medium and high voltage switches that are used in SaudiAramco is based on the technical, the installation, and the economic requirements of a facility.Facility switch technical requirements include the system voltage level and the normal andtransient current levels for the electric power system. Once the switch for a given installation isselected, the switch and the support equipment (e.g., mounting platform and terminationbushings) is ordered from the manufacturer, and it is then installed. The commissioning processfor medium and high voltage switches in Saudi Aramco facilities is a process that ensures that asafe and cost-effective system is installed that performs to the specifications of the facility for theprojected operating lifetime of the facility. Experience has shown that the time and the effort thatis expended upfront to ensure safety, quality control, and adherence to Saudi Aramco andindustry standards minimizes subsequent equipment failure.

The medium and high voltage switch commissioning process involves inspections, verifications,and checks that determine whether the switch specifications and installation requirements aremet. Tests are also performed that determine whether the electric power distribution system willoperate properly and safely once the switch is installed. When a medium or high voltage switch isinspected and tested satisfactorily during the commissioning process, the system should operate inaccordance with manufacturer's specifications for its maximum useful life.

This Module provides information on the following topics that are pertinent to commissioningmedium and high voltage switches for Saudi Aramco installations:

Saudi Aramco Requirements

Evaluating Medium/High Voltage Switches Upon Receipt

Evaluating Medium/High Voltage Switch Installation and Testing

System Pre-Operational Check-Out

System Operational Testing




SAUDI ARAMCO REQUIREMENTS

The basic operational function of a switch is to isolate power from a source to a load; however,with modifications or changes in construction, switches can have several different functions andcan be used to serve many purposes. Disconnect switches can be used to alter circuitarrangements and to provide electrical isolation for equipment that has to be removed fromservice for maintenance. Standard disconnect switches are designed to be opened and closed toisolate a single load or group of loads when no current flow is present.

A good example of the relationship between a standard disconnect switch and a circuit breaker isshown in Figure 1. Figure 1 shows a standard distribution bus that is fed by one generator. Eachfeeder has a circuit breaker and a disconnect switch. This type of bus configuration should onlybe used where interruptions to load service are unimportant because outages must exist to allfeeders simultaneously when the feeder bus, the generator breaker, or the generator is out ofservice for any reason. The circuit breaker provides protection against short circuits on the feederand enables the feeder to be removed from service, if necessary, while it is carrying load. Withthe breaker open, the disconnect switch serves as additional backup protection for personnelduring maintenance or repair work on the feeder. The disconnect switch also enables the feederbreaker to be isolated from the bus for inspection and maintenance on the breaker. Disconnectswitches are frequently arranged so that when the disconnect switch blades are opened, they areconnected to a grounded clip to prevent maintenance personnel from exposure to dangerousvoltage potentials.

The example that is shown in Figure 1 is of the Westinghouse type CA switchgear, which utilizeisolator switches in the configuration that is shown. This equipment is non-standard and will notbe used in future projects.




Figure 1: Disconnect Switch Use on Example Feeder Bus(Type CA Switchgear Arrangement)

With certain modifications, switches can also be used to isolate circuits under load. Switches thathave the capability to interrupt load current are commonly called loadbreak switches. Dependingupon the installation requirements, switches can also be fused or unfused. Fused switches provideadditional protection and coordination capabilities that enhance the versatility of switchapplication.




In addition to isolating a single load or group of loads, switches can be used to transfer power toa load from one source to another. The ability to transfer loads from a primary source of powerto an alternate source of power provides increased system reliability and continuity of power.Switches can also be used in a complex power distribution scheme that requires sectionalizing orthe multiple tapping of a primary feeder to serve transformers or laterals. In addition, specialapplication switches are available that can intentionally ground circuits, provide power fromstandby systems, or serve as a temporary circuit breaker replacement. Special applicationswitches are not covered in this Module.

The requirements for switches that are used for Saudi Aramco installations are found inSAES-P-116, Switchgear and Control Equipment, 16-SAMSS-510, Load Interrupting Switches0.6 kV through 38 kV, and related industry standards. The standard that is used as the basereference for 16-SAMSS-510 is the Pad-Mounted Switchgear and Load Interrupting Switchessection of IEEE C37. The IEEE C37 standard is a compilation of guides and standards that areused for circuit breakers, switchgear, relays, substations, and fuses.

Switches use either air, oil, or SF6 gas as the insulating (or interrupting) medium. The mostcommon types of switches that are used in Saudi Aramco installations are the air break switchesand oil-filled switches; however, because of industry advances in SF6 interruption technology, thecurrent trend is to replace oil-filled-type switches with SF6 types. Although many switches areavailable for power distribution applications, Saudi Aramco installations usually use the followingmanufacturers' switches:

ABB (SF6-type) RGC

G&W GRAM (oil-type)

S&C PMH-9-11-6 (oil-type)

Westinghouse WLI air break

GE air break

The two general types of switches that are found in Saudi Aramco installations are theindoor-type and the outdoor-type. Depending on whether the switch is used indoors or outdoors,the physical construction of a switch may be different, but the basic operational functions of theswitch will remain the same.

Indoor-Type

Indoor-type switches are used in indoor power distribution systems in switchgear. Saudi Aramcocommonly uses ABB-SF6 type switches. Westinghouse switches are generally used indoors asisolation switches.




Pad-mounted switchgear is an assembly in which all energized parts are insulated and completelyenclosed within a system that is grounded and shielded. Pad-mounted switchgear should use anenclosure that is suitable for the environment and that utilize tamper-resistant construction foroutdoor above-ground installation.

Figure 2 shows a one-line diagram of an S&C Model PMH-9 pad-mounted switch. The PMH-9is a fused switch that is commonly used in Saudi Aramco installations because it provides aprimary-selective service. With primary-selective service, one circuit serves as the preferredpower source for the load. The second power source remains available as the alternate source ofsupply. If the preferred source fails, switching operations are performed to provide power to theload from the alternate source. In Figure 2, the S&C Model PMH-9 pad-mounted switch is beingused to switch and protect three-phase transformer #1 and three-phase transformer #2. Thetransformers can be switched at the load (fused) side of the switch, and the loads can beselectively served from either of the two power sources.

Reference is made to the PMH-9 as an example of the switches currently used in Saudi Aramco;however, the PMH-9 and other oil switches are being replaced.

Figure 2: S&C Model PMH-9 Pad-mounted Switch




Figure 3 shows a typical, indoor-type, high voltage disconnect switch. The disconnect switch thatis shown in Figure 3 is a three-pole, vertical, motor-operated, loadbreak disconnect switch. Thefunction of the movable switch's operating blade is to make contact with the contact assembly andto provide a path for system current. The function of the arc extinction chamber is to suppressand dissipate any arc that forms when the switch is opened. The operating bar and the springassembly function together to control the movement of the movable operating blade, the arcingpin, the arcing pin cantilever, and the blade operating link for each of the switch phases. Thefunction of the terminals is to provide a connection point between the line and the load side of theswitch and the rest of the electrical system. The mounting insulators function to providestructural support and insulation to ground.

Figure 3: Three-Pole, Vertical, Motor-Operated, Loadbreak Disconnect Switch




The disconnect switch is opened by means of the operating mechanism, which, with the assistanceof the spring assembly, rotates the operating bar about its axis. As the operating bar rotates, eachblade's operating link acts to open its respective movable operating blade. As the contacts in themain contact assemblies part, the arc extinguishing chamber suppresses and dissipates any arc thatis formed. The arc extinguishing chamber in the example high voltage switch is an extra featureof the particular switch that is shown.

Figure 4 shows a cut-away operational view of a typical arc extinguishing chamber. Part A ofFigure 4 shows that as the arcing pin moves away from the stationary arcing contact during adisconnect switch opening operation, an arc is formed. Part B of Figure 4 shows that when thearcing pin slides from between the plates, the plates are forced against the arc. As the arcing pinclears the opening, the gas that is created in the arcing process is forced through the opening intothe expansion chamber, and the arc is extinguished.

Figure 4: Cut-Away View of a Typical Arc Extinguishing Chamber




Outdoor-Type

Outdoor-type switches are used in outdoor power sections of transmission or distributionsystems. Outdoor-type switches are usually pad-mounted air-interrupting switches. Pad-mountedoutdoor-type switches are an assembly in which all energized parts are insulated and grounded;however, all major components of the switch (e.g., blades and insulating supports) are exposed.For outdoor-type switches, Saudi Aramco commonly uses G&W switches. SGC-type fusedisconnect switches are generally used outdoors to meet isolation requirements.

Figure 5 shows a typical outdoor-type, single-pole, medium-voltage disconnect switch. Theswitch that is shown in Figure 5 is a vertical-break, outdoor air switch that is designed foroperation by either a manual or a motor operating mechanism. The spring assembly and the hingetie function together to position the main blade. The upper crank arm, the expansion linkassembly, and the lower bearing assembly function together to rotate the main blade about its axisto lock and unlock the main blade contact assembly. The stationary arc horn and the movable archorn function to dissipate the arc that is produced when the switch is operated. The threeinsulation stacks function to provide structural support and insulation to ground.

The disconnect switch is opened by means of the operating mechanism, which rotates theleft-most insulation stack of the disconnect switch that is shown in Figure 5. As the left-mostinsulation stack rotates, the upper crank arm and the expansion link assembly act to rotate themain blade about its axis. As the main blade rotates, the movable contact surfaces also rotate, andthey disengage from the contact assembly. As the left-most insulation stack continues to rotate,the upper crank arm and the expansion link assembly lift the main blade into the open positionwith the assistance of the spring assembly.




Figure 5: Typical, Single-Pole, Medium-Voltage Disconnect Switch




Figure 6 shows a close-up view of a typical, outdoor-type, single-pole, medium-voltagedisconnect switch contact assembly. In Figure 6, the main blade is shown in a partially openposition. The contacts in the contact assembly are spring-loaded so that, when the switch isclosed and when the main blade's movable contact surfaces are horizontal, the main blade islocked in place. As the switch opens, the movable arc horn and the stationary arc horn controland dissipate any arc that is formed.

Figure 6: Close-Up View of a Disconnect Switch Contact Assembly




EVALUATING MEDIUM/HIGH VOLTAGE SWITCHES UPON RECEIPT

Because disconnect switches that are chosen for a particular installation must provide the properoperation, protection, and maintenance capabilities, they are verified to ensure that they complywith Saudi Aramco and industry standards and practices. The minimum mandatory requirementsfor the design and construction of disconnect switches are provided in Work Aid 1.

The installation of a medium or high voltage switch is a process that takes place over a period oftime. The installation begins with an identified need for a switch installation (e.g., a new facility).Because power is necessary for critical loads at the new facility, a switch installation is designed.After the design is approved, the switch and the switch equipment (e.g., enclosures or switchgear)are ordered from the manufacturer. Once the switch is received from the manufacturer, it must beevaluated to ensure that it is proper for the installation. The purpose of the evaluation is to verifythat the correct switch was received from the manufacturer and that the proper installationspecifications and parameters are met. This section describes how medium and high voltageswitches are evaluated upon receipt.

Visual Inspection

When a medium or high voltage switch is received from the manufacturer, a visual inspectionmust be performed. The purpose of the visual inspection is to verify that the switch that wasreceived from the manufacturer is in good physical condition and that all of the requested partsand accessories are present. Because of the damage that can occur to the moving parts that areassociated with switches during installation, a cursory inspection is performed at the receivingpoint. During the cursory inspection, the inspection personnel look for obvious equipmentdamage and determine whether the necessary support equipment (e.g., manual operators andtechnical manuals) are present. A detailed inspection of the switch is performed when it iscompletely installed at the site or facility.

Verification Against Specifications

When a new facility or facility modification is at the equipment installation stage, the design of theinstallation has already been completed. The type of switch that is selected for a specific powersystem should be shown in the drawings, the prints, or the specifications for the installation. Thepurpose of verifying the switch against the specifications is to ensure that the equipment that isbeing installed meets Saudi Aramco and industry standards.




Generally, the verification against specifications consists of a determination of whether the typeand rating of the equipment that is to be installed match the size and the type of the equipmentthat is required for the installation. In some cases, this determination is accomplished by readingan electrical plan that identifies the switch size and type. The Electrical Engineer inspects themanufacturer's nameplate data on the switch and compares it to the requirements on the electricalplan to determine whether the correct equipment is being used. In other situations, the ElectricalEngineer must rely on his knowledge of the correct application of automatic transfer switch sizesand types to determine whether the correct equipment is being used. Any data sheets ormanufacturer information that were used to order the switchgear from the manufacturer must alsobe consulted. Any quality control, quality assurance, and test data that are provided with theautomatic transfer switch must also be reviewed.

Ratings and Nameplate Data

All pad-mounted switchgear that contain load interrupting switches that are used in Saudi Aramcopower systems should have a nameplate that is clearly visible on the front of the unit. Thenameplate should contain manufacturer and rating information. In accordance with ANSIC37.72, the manufacturer and the rating information that should appear on the nameplate of pad-mounted switchgear with load interrupting switches must include the rated frequency, the ratedmaximum voltage, the rated dielectric strength, and the current ratings.

Frequency Rating - Switches and electric power distribution systems are designed tooperate at a specific frequency. Saudi Aramco electrical distribution systems are designedto operate at 60 Hz.

Rated Maximum Voltage - Medium and high voltage switches are designed for andshould be marked with the rated maximum voltage. The rated maximum voltage is thehighest rms voltage above nominal system voltage for which the switch is designed, and itis the upper limit for operation. Voltage rating information is provided in Work Aid 1.

Rated Dielectric Strength - To test a switch to determine whether the dielectric strength(insulation level) is adequate to protect the switch against damage from lightning andother surges, the switch is impulse-tested. The basic impulse insulation level (BIL) is thereference impulse level, expressed in full wave kilovolts, that the switch can withstandwithout a flashover. The BIL is based on a test that uses a wave that is intended tosimulate a lightning stroke. The wave that is used for the test that is performed on aswitch is a 1.2 x 50 microsecond wave. The wave goes from zero to a crest voltage in 1.2microseconds, and the wave reaches a magnitude that is half of the value of the crestvoltage in 50 microseconds. In the tests, both positive and negative impulse voltages areapplied to the switch without damage or flashover. The wave crest value is equal to therated full wave impulse withstand voltage of the switch.




A low-frequency withstand voltage test is also performed on pad-mounted switchgear thatcontain load interrupting switches. The low-frequency withstand voltage test determinesthe ability to withstand a low frequency voltage for a period of time without flashover ordamage to equipment (e.g., bushings).

Current Ratings - Pad-mounted switchgear that contain load interrupting switches aredesigned for and should be marked with the continuous current that the switch is capableof carrying and the fault current values that the switch is capable of interrupting, withoutdamage to the switch. Specific current ratings are as follows:

Rated Continuous Current. The rated continuous current is the amount of currentthat the switch can continuously carry without exceeding the allowable temperaturerise.

Load Interrupting Current. The load interrupting current is the highest value of theload current that the switch can interrupt without damage from flashover andwithout exceeding the allowable temperature rise.

Short Time Currents. The short time currents are the highest values of momentary,making, and one-second currents that the switch can interrupt without damagefrom flashover and without exceeding the allowable temperature rise.

Magnetizing and Cable Charging Currents. The magnetizing and cable chargingcurrents are interrupting currents that the switch can withstand without damagefrom flashover and without exceeding the allowable temperature rise.




EVALUATING MEDIUM/HIGH VOLTAGE SWITCH INSTALLATION AND TESTING

The process to determine whether medium and high voltage switches should be commissioned isto verify that all the inspections and tests have been performed properly and to verify that the testresults are within the specifications that are designated by the applicable Saudi Aramco andindustry standards.

Installation inspections are performed to verify that proper medium and high voltage switchinstallation materials are used, that installation specifications and parameters are met, and thatproper installation procedures are followed. The installation inspection is conducted to ensurethat medium and high voltage switches and associated switchgear will function properly once theyare installed. Electrical tests are performed to check the ability of medium and high voltageswitches and any associated support equipment to function under all operating conditions andloads.

Installation tests should detect shipping or installation damage, gross manufacturing defects, orerrors in workmanship or installation. The Saudi Aramco Pre-Commissioning Form, P-021, SF-6Pad-Mounted Enclosure, contains guidance on the items that should be inspected, checked, andtested during the commissioning process.

A failure in any one of the many inspections, checks, or tests that are performed on medium andhigh voltage switches during the commissioning process is sufficient to prevent the equipmentfrom being commissioned. Because of the different inspection items that are associated withswitches, several courses of action are available for switches that have failed a visual inspection.The course of action depends on the part of the switch that failed the visual inspection. Someswitch parts (e.g., insulation support stacks) can be corrected through the replacement of theparts that failed the visual inspection. Visual alignment, mechanism/linkage, lubrication, orcleanliness inspection failures can usually be corrected through maintenance procedures. A visualphysical damage and suitability inspection failure will probably require the replacement of theentire incorrect or damaged part. For mechanical test and inspection failures, different courses ofaction may be required. For example, a bolt torque test failure can be corrected throughadjustment of the bolts with a torque wrench.

Because an electrical inspection or test failure can be caused by a construction error, equipmentage, or operational misuse, some type of troubleshooting or maintenance activity should beperformed on the switch when an electrical inspection or test is failed. Some electrical inspectionor test failures are not repairable, and such failed equipment must be replaced. A failure in anyone of the many tests that are performed on a switch during initial installation and commissioning,no matter how insignificant the test may seem, is sufficient cause not to allow the switch to beplaced in service. The inspector must be able to determine the appropriate action to take tocommission the switch.




The proper evaluation of inspection and testing data during the commissioning process canmaximize the operating time of equipment installations through a determination of trends towardsfailure. Failure prediction can drastically reduce equipment downtime. If a failure is predicted,operational changes can be made, maintenance can be performed, or equipment that is failing canbe replaced in a controlled manner. If a problem is corrected before it causes damage, operatingcosts will be lower because a malfunction will be prevented. Malfunctions can cause associated(or nearby) equipment damage, disruption of service, or the activation of emergency repair crews.

Visual Inspection

Visual inspections are used to assess the physical condition of medium and high voltage switches.A visual inspection is a pass/fail verification about a particular aspect of either the physicalcondition or the operation of medium and high voltage switches. P-001 contains guidance on theitems that should be checked during a visual inspection of medium and high voltage switches.Because the criteria that are established to determine the acceptability of the visual inspections canbe subjective, the visual inspections should be performed by an experienced Electrical Engineer.The following visual inspections are used to assess the condition of medium and high voltageswitches in Saudi Aramco systems:

Alignment

Contacts

Mechanism/Linkage

Three-Phase Contact Blades Make and Break Together

Physical Damage

Lubrication

Cleanliness

Suitability

Alignment

The purpose of the alignment inspection is to ensure that the medium voltage or high voltageswitch will properly pass current when it is connected to the rest of the electrical system and thatno improper connections are present. Improper alignment can cause uneven equipment heatingand wear. Proper alignment of the live disconnect parts (i.e., disconnect switch jaws, blades, andconnectors) ensures a proper electrical connection and minimizes adverse heating effects. Due tothe construction of switches, most of the parts are visible to inspection personnel, and the properswitch alignment, connections, and clearances will be evident.




The alignment visual inspection should be performed during the normal maintenance cycle ofswitchgear and medium and high voltage switches as determined by Saudi Aramco proceduresand practices. Technical data to evaluate the results of the alignment inspection can be found inthe switchgear and switch manufacturer's technical manuals.

Contacts

When a medium or high voltage switch is connected to the electrical system and is closed, thecontacts provide a current path through the switch. The contacts must also withstand currentlevels that occur when the switches are opened under load. Damage can occur at the contacts asa result of the mechanical stress from closing operations and from the electrical arc that formsduring contact opening operations. The purpose of the visual inspection of the contacts is toensure that they provide a low resistance current path and that the contacts of medium and highvoltage switches can safely interrupt load current and can be closed under load.

Small burn and pock marks can develop on the surface of the contacts over the operating life of aswitch. Such marks will not interfere with the operation of the contacts, but the contacts willneed to be replaced when they erode over time to some wear point that is defined by themanufacturer. For medium and high voltage switches that have arc extinction chambers (e.g., air,oil, or vacuum), a contact wear indicator is checked.

The visual inspection of the switch contacts should be performed during the normal switchgear orswitch maintenance cycle as determined by Saudi Aramco procedures and practices. The moststringent of the applicable maintenance cycles is the cycle that should be applied. Technical datato evaluate the results of the contact visual inspection can be found in the switchgear or switchmanufacturer's technical manual.

Mechanism/Linkage

The mechanism/linkage assembly of medium and high voltage switches performs the actualmovement of the switch contacts during open or close operations. The purpose of themechanism/linkage inspection is to ensure that the mechanism/linkage can move freely. Freemovement of the mechanism/linkage will ensure that the switch can be properly operated by theoperator (or operating mechanism). The inspector should visually determine that no obstructionsexist that will restrict or impede the proper operation of the mechanism/linkage.

The mechanism/linkage visual inspection should be performed during the normal maintenancecycle of switchgear and switches as determined by Saudi Aramco procedures and practices. Themost stringent of the applicable maintenance cycles is the cycle that should be applied. Technicaldata to evaluate the results of the mechanism/linkage visual inspection can be found in theswitchgear and switch manufacturer's technical manuals.




Three-Phase Contact Blades Make and Break Together

When three-phase medium or high voltage switches operate, the contacts must open and close asa group. Additionally, the arcing contacts (and the arc horn, if used) must make and break insequence with the main movable blade contacts during switch operations. The proper contactmake and break should be observed during the open/close operation test. Proper contact makeand break consists of both the physical contact operation and the sequence of the contactoperation.

The three-phase contact blades' make and break visual inspection should be performed during thenormal maintenance cycle of the switches as determined by Saudi Aramco procedures andpractices. The most stringent of the applicable maintenance cycles is the cycle that should beapplied. Technical data to evaluate the results of the three-phase contact blades' make and breakvisual inspection can be found in the switch manufacturer's technical manual.

Physical Damage

Physical damage of switches can prevent the proper operation of protective equipment (e.g., archorn failure), or it can lead to dangerous system grounds or shorts. Because of the magnitude ofthe electric energy that passes through medium or high voltage switches and the installedinterrupting devices and because of the large forces that are required to open and close switches,any physical damage to switches can propagate and will often require major equipmentreplacement. The most obvious and common forms of physical damage are cracks, dents, andmissing or broken pieces. The switch blades should be checked for warps, distortions, or bentstructural framework.

The purpose of the physical damage inspection is to identify whether corrective maintenance orequipment replacement is necessary due to physical damage. The physical damage inspection ofthe medium or high voltage switch must include any and all equipment that is contained orattached to the switch. Medium and high voltage switches (and the support equipment) that showany form of physical damage, no matter how small, should be determined to have failed thephysical damage inspection.

The physical damage visual inspection should be performed during the normal maintenance cycleof switchgear and switches as determined by Saudi Aramco procedures and industry practices.The most stringent of the applicable maintenance cycles is the cycle that should be applied.Technical data to evaluate the results of the physical damage visual inspection can be found in theswitchgear and switch manufacturer's technical manuals.




Lubrication

The lubrication visual inspection should be performed in conjunction with the mechanism/linkagevisual inspection. The purpose of the lubrication visual inspection is to ensure that all movingparts, bearing points, and sliding mechanisms of the medium or high voltage switch are properlylubricated and free of rust.

Before the application of new lubrication can take place, hardened grease, dirt, and rust should beremoved from the surfaces that require lubrication. A cloth that is dampened with keroseneshould be used to remove the hardened grease and dirt. Care must be taken to ensure that thecloth does not deposit fibers on the moving parts. The deposit of cloth fibers on moving parts cancause subsequent improper mechanism operation. After the proper preparation of the movingparts, a thin layer of lubrication should be applied. Excess lubrication should be wiped off with aclean cloth.

The lubrication visual inspection should be performed during the normal maintenance cycle ofswitchgear and switches as determined by Saudi Aramco procedures and industry standards. Themost stringent of the applicable maintenance cycles is the cycle that should be applied.Lubrication of the switches is acceptable if it allows free range of motion of the switch parts and ifthe lubrication is not hard. Technical data to evaluate the results of the lubrication visualinspection can be found in the switchgear and switch manufacturer's technical manuals.

Cleanliness

The purpose of the cleanliness visual inspection is to ensure the proper operation of the mediumor high voltage switch over the maximum operating life. The accumulation of dirt (over a periodof time) in a switch will impede the proper operation of the switch and the installed protectiveequipment, and the accumulation of dirt will reduce the dielectric strength of the insulation stacksand mountings.

To maintain the proper operation of the switch, the accumulation of heavy amounts of dust shouldbe cleaned away from the switch during maintenance cycles. Inspections should be performedboth before and after cleaning or dust removal is conducted. For switches that are installed inswitchgear or enclosures, telltale signs can be left in dust that can reveal otherwise hidden adverseconditions. For example, moisture droplets can leave small craters in dust. Dust can also maskadverse conditions. For example, a carbon track that exists on a bus support may be completelyhidden under a layer of dust.




The cleanliness visual inspection should be performed during the normal maintenance cycle ofswitchgear and switches as determined by Saudi Aramco procedures and industry practices. Themost stringent of the applicable maintenance cycles is the cycle that should be applied. Switchesthat are installed in extremely dirty, dusty, or humid areas may have to be cleaned more often thanonce during the normal maintenance cycle. Dirt or dust should be cleaned away when, in theopinion of the person who performs the maintenance, the dirt or dust would impede the switchoperation.

Suitability

The purpose of the suitability visual inspection is to determine whether the medium or highvoltage switch is appropriate for the application in which it is placed. To determine the suitabilityof a switch, a visual inspection of the nameplate information on the switch should be performedand compared to the known information about the electrical system in which the switch is placed.If the nameplate information does not match the ratings of the electrical system, the switch shouldbe replaced. Although the suitability inspection of the switch is usually performed duringcommissioning, it should also be performed during the normal maintenance cycle of the switch asdetermined by Saudi Aramco procedures and industry standards. Periodic visual inspectionsshould be performed to ensure that changes that may have been made to the system have notexceeded the ratings of the disconnect switch. The most stringent of the applicable maintenancecycles is the cycle that should be applied. Technical data to evaluate the results of the suitabilityvisual inspection can be found in Saudi Aramco and industry standards as well as in the switchmanufacturer's technical manual.

Mechanical Inspections and Tests

Mechanical inspections and tests are used to assess the ability of a medium or a high voltageswitch to physically perform the mechanical movements that are necessary to make or to break anelectric circuit. The mechanical inspections and tests also assess the safety functions (e.g., keyinterlock) of the switch. The mechanical inspections and tests that are performed on medium andhigh voltage switches that are installed in Saudi Aramco systems are as follows:

Open/Close Operation

Arcing Horns Function

Bolt Torque

Contact Wipe

Mechanical Locking of Contact Blades

Key Interlock System Operation




Open/Close Operation

Some medium or high voltage switches in Saudi Aramco electrical systems can go frommaintenance cycle to maintenance cycle without a single operation. A switch must always be in acondition to operate, no matter how infrequently the switch has been used. The purpose of theopen/close operation test is to ensure that the switch opens and closes properly.

To perform the open/close operation test, the switch is cycled from the fully open position to thefully closed position and back to the fully open position. During the closing and openingoperations, the mechanical condition of all of the connected devices (e.g., arc horns and positionindicators) is checked for proper operation. For medium or high voltage switches withinterruption chambers in which the contacts are not visible, the manufacturer's technical manualshould contain information on the minimum moving contact travel distances.

The open/close operation test should be performed during the normal maintenance cycle of amedium or high voltage switch as determined by Saudi Aramco procedures and practices. Themost stringent of the applicable maintenance cycles is the cycle that should be applied. Technicaldata to evaluate the results of the open/close operation test can be found in the switchmanufacturer's technical manual.

Arcing Horns Function

Medium and high voltage switches can contain arc horns, arc chutes, arcing tips, arcing boxes, ora combination of all of these arc-suppression devices. The arc horns direct developed arcs awayfrom the switch contact assembly, which prevents damage to any connected or adjacentequipment. The purpose of the visual inspection of the arc horns (and other arc-suppressiondevices) is to ensure that the arc horns can safely suppress the arc that forms when the switchopens. The arc horns (or arcing tips) should be adjusted so that the arcing devices close beforethe main contacts close and open after the main contacts open. During the visual inspection, thearc horns (or arcing tips) should be inspected for pitting or scoring that could prevent the arc hornfrom properly directing the developed arc.

If the medium or high voltage switch uses an arc chute or an arc extinguishing chamber, the chuteor chamber should be inspected for burn marks, scale, and cracks. Burn marks change theconsistency of the surface of an arc chute. If burn marks are present on an arc chute, the arcchute should be replaced. Scale is the accumulation of foreign material in the arc chutes that canimpede the ability of the arc chutes to extinguish an arc. Scale should not be removed from thesurface of the arc chutes; so, the inspector must determine whether the scale will impede theability of the arc chute to extinguish an arc. If the inspector determines that the scale will impedethe ability of the arc chute to extinguish an arc, the arc chute is replaced. Cracks form in the arcchutes during the normal operation of a switch. The inspector must determine whether the crackswill interfere with the ability of the arc chute to extinguish an arc, and he should replace the arcchute accordingly.




Oil-filled switches are also used for medium and high voltage switch applications. Oil-filledmedium and high voltage loadbreak switches are commonly used by Saudi Aramco for industrialapplications. Oil-filled switches are only suitable for outdoor use. For high making and breakingcapacity, the oil-filled switch should incorporate either a spring toggle mechanism or some formof arc control. The preferred type of switch construction has spring toggle mechanisms that areenclosed inside the tank. Regular inspection and maintenance of oil-filled switches are necessaryto remove accumulated sludge and to test the quality of the oil.

The visual inspection of the arc suppression device (e.g., the arc horn) should be performedduring the normal maintenance cycle of a switch as determined by Saudi Aramco procedures andpractices. The most stringent of the applicable maintenance cycles is the cycle that should beapplied. Technical data to evaluate the results of the arc suppression device visual inspection canbe found in the switch manufacturer's technical manual.

Bolt Torque

The terminations of most medium and high voltage switches use bolted connections. Medium andhigh voltage switch supports and movable blades use bolted metal segments. For a given switchinstallation, many connecting bolts must be installed. Each bolt has a torque specification thatshould be met for the installation. During the evaluation of the switch installation, the ElectricalEngineer should spot test the torque on the connecting bolts.

When the spot test of the connecting bolts is performed, the Electrical Engineer should check thatall bolted connections have the correct hardware (e.g., washers and nuts) installed. The purposeof a bolt torque inspection is to ensure that enough force is present to hold the bolts in placeduring all required operations. To determine the amount of force that exists at a bolt, a torquewrench is applied to the bolt in the direction that will tighten the bolt, and the amount of torque isread.

The bolt torque inspection should be performed during the normal maintenance cycle of mediumand high voltage switches as determined by Saudi Aramco procedures and industry practices. Themost stringent of the applicable maintenance cycles is the cycle that should be applied. Technicaldata to evaluate the results of the bolt torque inspection can be found in the Saudi AramcoPre-Commissioning Form, P-000, Testing Guidelines, as well as the switch manufacturer'stechnical manual. Bolt torque values are provided in Work Aid 2.




Contact Wipe

The purpose of the mechanical inspection of the contact wipe is to ensure that the correct contactwipe is present at the switch contacts. The contact wipe should be observed and measured duringthe open/close operation test of switches. The contact wipe is the distance that the stationarycontacts move as the switch main contact blade moves from the open to the closed position. Allvarious switch main contact assembly designs require that specific pressures be kept on themovable blade contacts to ensure proper electrical contact. The contact pressure is usually afunction of the travel distance of the stationary contacts after the tips touch during a closingoperation.

The contact wipe inspection should be performed during the normal maintenance cycle of a switchas determined by Saudi Aramco procedures and practices. The most stringent of the applicablemaintenance cycles is the cycle that should be applied. Technical data to evaluate the results ofthe contact wipe inspection measurements can be found in the switch manufacturer's technicalmanual.

Mechanical Locking of Contact Blades

If the medium or high voltage switches are provided with a locking feature, a mechanicalinspection and test should be performed on the mechanical locking jaws of switches. The purposeof the mechanical inspection and test of the mechanical locking feature of a switch blade is toensure that the blade contact locks into place when the switch is closed and to test that thelocking feature releases the blade when the switch is opened. The inspection and test of themechanical locking feature is performed by cycling the switch and by observing the properoperation of the locking feature. For gang-operated switches, the inspection and test personnelshould also determine that each phase makes connection and that the locking jaws locksimultaneously.

The mechanical inspection and test should be performed on the mechanical locking feature duringthe normal maintenance cycle of a switch as determined by Saudi Aramco procedures andpractices. The most stringent of the applicable maintenance cycles is the cycle that should beapplied. Technical data to evaluate the results of the mechanical locking feature inspection andtest can be found in the switch manufacturer's technical manual.




Key Interlock System Operation

Disconnect switches are usually associated with a circuit breaker or switchgear installation. Whena disconnect switch is in series with or associated with a circuit breaker, an interlock should beused to prevent the opening of the disconnect switch with the breaker closed. The interlock cantake the form of mechanical linkages, electrical relaying systems, or key interlocks. Keyinterlocks are an inexpensive way to prevent the inadvertent operation of disconnect switches.

Figure 7 shows an example application of loadbreak switches in a high voltage system with keyinterlocks. In Figure 7, the loadbreak switches are used to sectionalize loads between twoalternative feeders in a loop network. The "X" sectionalizing loadbreak switches provideoperational and load division switching. It is normal to operate such a system with one end open,in which case a fault will be cleared by the operation of one of the "Y" breakers. The faultysection can then be isolated, and the supply can be restored to the rest of the system.

Key interlocks (Kirk-Key) may be used on manually operated schemes to prevent inadvertentparalleling of the two different supply feeders (i.e., the preferred and the emergency supply). Forboth the "X" and "Y" switches, one set of keys is available for each switch pair. Because only onekey is provided for each pair, only one of the two switches in each pair can be closed at any onetime.




Figure 7: Example Application of Disconnect Switch Key Interlocks

Switches that use key interlocks may be in parallel, or they may be associated with parallel powersources. Because a switch with a key interlock can only be operated when the key is inserted, andbecause only one key is provided for each pair of switches, both switches cannot be operated atthe same time. If both switches cannot be operated simultaneously, the inadvertent paralleling ofpower sources is physically impossible. The removal of the key can render both switchesinoperable during troubleshooting or maintenance evolutions.




The purpose of the mechanical operation inspection is to ensure that the key interlock system willfunction properly. The basic method that is used to perform this inspection is to attempt tooperate both switches at the same time. Extreme caution must be exercised when this test isperformed. The entire system should be deenergized prior to the test to prevent serious injury topersonnel or damage to equipment in the event that the interlock does not function properly. Theresults of the key interlock system mechanical operation inspection are satisfactory if the interlocksystem is visually observed to properly operate.

Electrical Tests

Electrical tests are performed to check the ability of switches to operate for a reasonable futureperiod of time under all operating conditions and loads. Acceptance or installation tests willusually detect shipping or installation damage and gross defects or errors in workmanship inswitch construction. Maintenance tests are performed at periodic intervals during the operatinglife of a switch. The following electrical tests are performed on Saudi Aramco switches:

Contact Resistance

Insulation Resistance

Oil Dielectric

High Potential

Contact Resistance

The purpose of the contact resistance test of a medium or high voltage switch is to identifycontacts that are defective or detrimental to the operation of the switch. The contact resistancetest may also identify loose connections in a switch. With the system deenergized and isolated,the leads of a digital, low-resistance ohmmeter should be placed across line and load sides of theswitch blade, and measurements should be taken across the contacts of each phase. A digital,low-resistance ohmmeter can deliver enough power to the switch to make accurate readings thathave more validity than those readings that can be obtained through the use of an ordinarymultimeter. The contact resistance is recorded on a test data sheet, and it is attached to the SaudiAramco Pre-Commissioning Form, P-001, Switches; High and Medium Voltage Air, Oil, andSF-6.

Increased contact resistance may be caused by contacts that do not make proper contact or bypitting on the surface of the contacts. The contact resistance values that are recorded should beconsistent with the manufacturer's recommended values. Generally, values of contact resistancein excess of 150 micro-ohms and deviations of more than +/- 20% between adjacent poles orsimilar switches should be investigated. Technical data to evaluate the results of the contactresistance test can be found in the switch manufacturer's technical manual.




Insulation Resistance

The purpose of the insulation resistance test is to directly measure the insulation resistance of themedium or high voltage switch through use of a megger. In the insulation resistance test, themegger is used to set up an electromagnetic field, and the field that is created is used to produceleakage currents that will flow through the insulation between each phase and ground or fromphase to phase. The amount of leakage current flow that is detected by the megger results in amegger meter readout of insulation resistance (in megohms).

To conduct the insulation resistance test, the megger is connected between two of the blades ofan open switch, and the megger is operated. Megohmmeter test voltages vary for medium andhigh voltage systems. Manufacturer's technical manuals should be consulted for the propermegohmmeter test value. In general, the values of insulation resistance should be less than themanufacturer's minimum values or less than the rated voltage of the system + 1 kV in megohms.Insulation resistance evaluation information is provided in Work Aid 2. Similar megger readingsare taken between each remaining phase pair combination on both sides of the open contacts ofthe switch. The megger is then connected between each switch blade and ground, and the meggeris operated. Similar megger readings are taken between each remaining phase and groundcombination on both sides of the open contacts of the switch. The insulation resistance values arerecorded on a test data sheet or in the Saudi Aramco Pre-Commissioning Form, P-001, Switches;High and Medium Voltage Air, Oil, and SF-6.

Acceptable insulation resistance values should be determined through use of the switchmanufacturer's technical manual. The insulation resistance test should only be performed duringthe commissioning of switches and during the first few maintenance cycles. After a fewmaintenance cycles, the hi pot test is used to determine the integrity of the insulation of theswitch.

Oil Dielectric

Oil is used in some medium and high voltage switch installations as the arc quenching medium.The oil that is used as an arc quenching medium must have the ability to insulate the contacts, toquench the arc, and to dissipate the heat that is formed when the arc is developed. Because of theimportance of the oil in the operation of switches that use oil, certain tests should be performedon the oil upon initial installation and during periodic maintenance periods.




The purpose of the electrical tests and inspections that are performed on insulating oil is to ensurethat the insulating oil has the correct dielectric properties to perform the arc interruption and thatno impurities are present in the oil. A large array of testing is performed on oil prior to shipmentand upon receipt; however, these tests generally fall into two categories: electrical tests of the oil'sdielectric properties and tests for the presence of impurities. The electrical tests of the oil'sdielectric properties test the dielectric breakdown voltage and the power factor of the switch oil.Tests for the presence of impurities, such as moisture and gas, are performed because thepresence of impurities in the oil has a negative impact on the dielectric properties of the oil. Theapproved methods that are used to perform each of the tests are provided by the AmericanSociety of Testing and Materials (ASTM). ANSI C57.106 - 1991 contains the ASTM testreference information and the technical data that are necessary to evaluate the results of the oildielectric inspection and tests.

High Potential

Both ac and dc high potential (hi pot) tests can be performed on medium and high voltageswitches and switchgear. The purpose of the ac hi pot test is to evaluate the condition of themedium or high voltage switch insulation. Insulation that is in good condition will have sufficientdielectric strength to withstand voltage surges that are caused by switching or transient linesurges. The ac hi pot test is used during the maintenance cycles of the switch to verify the propercondition of the switch insulation. The ac hi pot test is a go/no-go test, and it will not identifyinsulation that is gradually deteriorating.

In general, the ac hi pot test can be performed on the same test points as the insulation resistancetest; however, the frequency with which the ac hi pot test is performed differs from the insulationresistance test. The ac hi pot test is performed through the use of an ac hi pot test set. The leadsof the test set are applied to the same test points as the leads in the insulation resistance test. Themanufacturer's technical manual must be consulted to determine the appropriate test voltage forthe test.

Once the appropriate test voltage has been determined, it should be applied to the switch to testthe insulation for a period of one minute. The ac hi pot test set measures the amount of currentthat leaks through the insulation of the medium or high voltage switch. When the leakage currentreaches a predetermined amount, an overcurrent relay inside the test set is actuated, and a light islit on the test set that indicates insulation failure. Sparks or arcs around the test leads alsoindicate insulation failure. If any of these test conditions occur, the switch needs to be replaced.




The purpose of the dc overpotential (hi-pot) test is to identify internal faults in or damage to theelectrical insulation. The dc hi-pot test should be performed prior to the initial energization of amedium or high voltage switch and after the megohmmeter test. The dc hi-pot testing techniqueinvolves increased dc voltage that is applied to the system under test. The value of the leakagecurrent is measured and tracked as the test voltage is increased through several steps. This valuebecomes a criterion of the condition of the insulation.

Electrical test reference information for the ac and dc hi-pot tests is provided in the Saudi AramcoPre-Commissioning Form, P-000, Testing Guide Lines. The electrical test reference informationprovides the recommended test procedure and test voltages for the various equipment voltageratings. During the test, the leakage current is plotted against time at the end of each timinginterval.

The ac or dc hi-pot test information is recorded on a test data sheet or in the Saudi AramcoPre-Commissioning Form, P-001, Switches; High and Medium Voltage Air, Oil, and SF-6. Acand dc hi-pot test evaluation information is provided in Work Aid 2. The Electrical Engineershould evaluate the ac and dc hi-pot test leakage current test data to ensure that the test data meetthe minimum requirements for a successful test. A polarization index value of two or greater orac or dc hi-pot test data curves that indicate a steady increase in leakage current over the durationof the test should be investigated by the Electrical Engineer who performs the test dataevaluation.




SYSTEM PRE-OPERATIONAL CHECK-OUT

The system pre-operational check-out phase of the commissioning cycle for medium and highvoltage switches provides an opportunity for Saudi Aramco personnel to perform wiring checks,subsystem component check-outs, and switch interlock performance tests. Each medium and highvoltage switch component is checked to ensure that it works individually and as a completesystem.

Point-to-Point Wiring Check

Point-to-point wiring checks are performed to verify medium and high voltage switch compliancewith wiring diagrams and manufacturer specifications. Terminations and terminal blocks are alsochecked for routing and labeling. During the point-to-point wiring checks, terminations,supports, and fuses are checked for proper application and type.

Subsystem Check-Out

Subsystems are checked to ensure that electrical continuity exists for operational and controldevices. The proper operation of all subsystems is tested by means of the controlled operation andcheck-out of the devices. An example subsystem operation and check-out is to operate the motorof a three-phase, motor-operated, disconnect switch. Each subsystem is performance testedthrough the application of full operational voltage to each subsystem through the properprotective devices (if applicable). A complete operational test is performed on equipmentcontrols, interlocks, protective devices, and components with each subcircuit connected to itsmain system. During the performance test, the main systems are still isolated and independentfrom plant systems. Before the equipment is connected to the plant system, subsystemperformance testing is critical to ensure the proper and safe operation of the equipment protectionand control subsystems.

Because phasing of power supplies is critical to the proper operation of rotating equipment loads(e.g., pumps and motors), the proper phase sequence at each of the power supply terminals mustbe checked and verified against the phase sequence of the connected loads.

Interlocks

Operation tests are performed to ensure that the medium and high voltage switch operationalinterlocks function properly. For example, if the switch has a key interlock, the proper operationof the key interlock should be tested. When a key interlock is tested, it should be tested to ensurethat operation of the switch is possible with the key and that operation of the switch is notpossible without the key. Any other operational interlock devices on the switch that can preventthe operation of the switch should be tested in a similar manner.




SYSTEM OPERATIONAL TESTING

The operational testing phase of the commissioning cycle for medium and high voltage switchesprovides an opportunity for Saudi Aramco personnel to perform the following:

Source Feed Compatibility Checks

Complete System Functional Test

Source Feed Compatibility

Source feed compatibility checks are performed on medium and high voltage switches throughapplication of the full system voltage onto the installed medium or high voltage switch. With thevoltage applied, voltage phasing, synchronizing, device rotation, and other source feedcompatibility checks are performed. Both the preferred and the emergency power sources areconnected to the loads to ensure the total operation of the major component loads of the system.

Complete System Functional Test

The operational testing of a medium or high voltage switch ensures that all of the installed parts,such as linkages and jaws, are able to work in conjunction with each other so that the switch andthe installed equipment can provide electrical system protection and operation. Most of the teststhat have been performed thus far have been tests that ensure the performance of the individualparts of the switch. The complete system functional test will ensure that the parts will worktogether so that the switch will operate correctly when it is installed in an electrical system.

A complete system functional test is performed on medium and high voltage switches to ensurethat the entire electric power system functions in accordance with the system design. During thecomplete system functional test, the equipment is allowed to assume a fully loaded condition for aperiod of time that is adequate to obtain the maximum system temperature. After the loaded timeperiod, the equipment temperatures are monitored. Equipment temperatures can be monitoredlocally through use of temperature monitoring equipment or through use of thermographicsurveys. Temperature monitoring equipment can be temporarily installed at the enclosure orswitchgear vents. Particular attention should be paid to wiring and terminal connections duringthe complete system functional test.




Because there may be several ways to operate a switch (e.g., manually by hand or with anoperating motor), each mode of operation must also be tested to ensure that it properly functions.The complete system functional test must also include the proper operation of all interlocks (e.g.,key interlocks) that are associated with the switch. The complete system functional testinformation is recorded on a test data sheet or in the Saudi Aramco Pre-Commissioning Form,P-001, Switches; High and Medium Voltage Air, Oil, and SF-6. During the complete systemfunctional test, the inspector should visually assess that all of the contacts of the switch haveopened as far as possible without grinding, scraping, or motion restrictions.




WORK AID 1: REFERENCES FOR EVALUATING MEDIUM/HIGH VOLTAGESWITCHES UPON RECEIPT

The information that is presented in the checklists and information tables has been assembledfrom SAES-P-116, 16-SAMSS-510, ANSI C37, GI-2.710, and related industry standards.

Figure 10 shows a table of Saudi Aramco general requirements for manually operated, dead-front,pad-mounted switches that are equipped with either separable connectors or other terminatingmeans for ac systems.

GeneralRequirements

Either separable connectors or other buyer specified means may be used toterminate the cable at a load interrupting switch.All energized parts of a dead-front pad-mounted switchgear (PMSG) mustbe insulated and completely enclosed within a grounded shielded systemwhen separable connectors are in place.The Vendor must provide equipment that is sufficiently derated to operate atnameplate rating under the following temperature conditions (in addition tothe temperature rise that is caused by Vendor's supplied equipment when it isoperating at the nameplate rating):

Monthly Normal Maximum Ambient Temperature:45 deg C Enclosure Internal Temperature Rise Due to:

(a) Solar Effects: 8 deg C(b) Internal Heater (if applicable): 3 deg C

Total 56 deg CEquipment that is supplied in accordance with 16-SAMSS-510 must beprotected from corrosion and operational failure when operating under thefollowing conditions:

Normal air-borne dust concentration must be considered as 1 mg/m3with 95% of all dust particles being less than 20 micrometer diameter.

Compounds present in the dust include those of sodium, calcium,magnesium, silicon, and aluminum.

Other pollutants present (worst case): H(2)S 20 ppm, SO(2) 10 ppm,CO 75 ppm, (NO(x) 5 ppm, and hydrocarbons 100 ppm.

Figure 10: Saudi Aramco Requirements forPad-MountedSwitchgear with Load-Interrupting Switches




Figure 11 shows Saudi Aramco load interrupting switch voltage ratings.

Rated Maximum Voltage (kV) Rated WithstandImpulse

3 Switches 1 Switches Voltage, kV

15.5 8.9 95

27 15.5 125

38 21.9 150

Figure 11: Voltages and Insulation Levels for Load Interrupting Switches(From ANSI C37.72 - 1987)

Figure 12 shows Saudi Aramco load interrupting switch load, cable charging, and magnetizinginterrupting ratings.

RatedMaximum 3

Switches

Voltage - kV1 Switches

Continuous andLoad Interrupting

CurrentAmperes, rms

Cable ChargingInterrupting

Current,Amperes, rms

MagnetizingInterrupting

Current,Amperes, rms

15.515.5

8.98.9

600200

1010

21 7

2727

15.515.5

600200

1515

21 7

3838

21.921.9

600200

2020

21 7

Figure 12: Load, Cable Charging, and Interrupting Current Ratings(From ANSI C37.72 - 1987)




Figure 13 shows a table of Saudi Aramco guidelines for the application and the selection of loadinterrupting switches.

GeneralRequirements

Load interrupting switches must not be used except with the prior writtenapproval of the Manager, Saudi Aramco Power Distribution Department.Pad-mounted switchgear (PMSG) with load interrupting switches must bedesigned, rated, manufactured, and tested in accordance with the latestissue or revision of ANSI/IEEE Standard C37.72 - 1987 or IEC 298.Rated insulation levels and current ratings that are applicable to air switchesmust be in accordance with ANSI C37.32 or IEC 298.All switches must be group-operated.Switch operating mechanisms must be protected from damage due toweather, dust, and corrosion. For outdoor units, the switch mechanisms,linkages, and springs should be located inside tanks or enclosures.Synchronism check devices must be provided in situations where it ispossible to interconnect two systems out of synchronism.For industrial applications, a blown fuse should initiate the opening of anassociated switch.Switches must be of dead-front construction.

OperationalRequirements

Load interrupting switches must be capable of breaking currents that areequal to the continuous current rating of the switch at the rated systemvoltage and load.Load interrupting switches must be capable of interrupting small inductiveor capacitive currents for applications in which the switch is used todisconnect unloaded transformers, cables, or overhead lines.Load interrupting switches must be capable of performing a closingoperation onto a terminal short circuit.Load interrupting switches must have independent operators.

Figure 13: Guidelines for the Application and Selection of Load Interrupting Switches




Figure 14 shows the construction requirements for medium and high voltage switch types from16-SAMSS-510, ANSI C37.72 - 1987, and ANSI C37.32.

Frame-MountedLoad

The frame-mounted load interrupting switch (oil-filled) is only suitable foroutdoor use.

Interrupting Cable terminations must be of dry-type, dead-front construction.Switch Potheads must not be used.

(Oil-Filled) The cable type must be specified by the purchaser so the switchmanufacturer can furnish the correct terminal parts.For high making and breaking capacity, the switch must incorporate either aspring toggle mechanism or some form of arc control.Regular maintenance of this type of switch is necessary to removeaccumulated sludge and to test the quality of the oil.Askarel or any polychlorinated biphenyl (PCB) dielectric (insulating fluid)must not be used.

Pad-MountedSwitches

Refer to 16-SAMSS-510 for pad-mounted load interrupting switchspecification requirements.Pad-mounted switchgear that uses switches in gas-filled sealed tanks ispreferred over air-insulated switchgear.Vacuum switches are the preferred type of switching device in pad-mountedswitchgear.Cable terminations must be dead-front, 600 A, separable, insulatedconnectors (elbows).Two threaded 1/2 in., #13 National Course (NC) bosses must be provided atopposite sides of the enclosure.Switch operating handles must be able to be padlocked in any position.Switchways must be provided with three positions.For switches that have on, off, and ground positions, the ground positionmust have the same withstand rating as the main switch.The switch mechanism must be such that switching from on directly toground is not possible. Switching must be from on to off and then from offto ground. A separate interlocked ground switch may be provided to meetthis switch mechanism requirement.The moving parts of switch operating mechanisms (e.g., springs) must belocated inside the switch enclosure and protected from exteriorenvironmental conditions.Switches that include a ground position must provide position indication thatis similarly distinctive to the open and closed positions.

Figure 14: Construction Requirements for Medium and High Voltage Switch Types




Pad-MountedSwitches

Bolts, hinges, and associated hardware must be of Type 300 Series stainlesssteel.

(Continued) Mounting frames and enclosing panels must be constructed of boltedgalvanized steel.Gasketing materials and adhesive must be suitable for the environmentalconditions specified in 3.2.1.All exterior surfaces must be painted and must meet the requirements ofANSI C57.12.28 - 1988, Pad-Mounted Equipment - Enclosure Integrity,Section 5 - Enclosure Coating System, except the paint color mustpreferably be white with light grey an acceptable alternative.Nameplate(s) must be on the side of the enclosure.The following information must be included and may be on a separatenameplate:

1) Buyer's purchase order number2) Manufacturer's location3) Manufacturer's order reference number

Nameplates must be in the English language according to American usage.Danger and warning indicators must be written in both Arabic (Naskh script)and English, utilizing white characters on a red background.

Metal-EnclosedInterrupterSwitchgear

Outdoor use of air-insulated interrupter switchgear is not allowed in newSaudi Aramco installations.

Figure 14: Construction Requirements for Mediumand High Voltage Switch Types (Contd)




For consistency, rated insulation levels and fault-make ratings that are applicable to air switches(as defined in ANSI C37.32) must be used for loadbreak switches. Figure 15 shows the preferredratings for medium- and high-voltage loadbreak switches that are used by Saudi Aramco.

Rated Withstand Voltage Current Rating (amperes, rms)Interrupting and Continuous

RatedMaximumVoltage(kV rms)

Impulse1.2x50msWave(kVCrest)

60 Hz kV rms 200 400 600 1200

Wet(10Sec)

Dry(1 Min)

Fault Make and MomentaryAsymmetrical Current Ratings, kA,rms1

4.76 60 15 19 20 20 40 618.25 75 24 26 20 20 40 6115.0 95 26 36 20 20 40 6115.5 110 30 50 20 20 40 6125.8 125 40 60 -- 20 40 6138.0 150 -- 80 -- 20 40 61

1 Short-time current ratings include a momentary and a three-secondcurrent rating that is based on test conditions that are described insection 5 of ANSI/IEEE C37.34. Divide the momentary rating by 1.6 toobtain the three-second current rating. When a higher momentarycurrent rating than is shown is required, use a switch that has the nexthigher continuous current rating.

Figure 15: Load Interrupting Switch Preferred Ratings (From C37.32-1990)




Medium and High Voltage Load Interrupting Switch applications Checklist

Medium and high voltage switch rating information can be found on the equipment nameplate orin the switch manufacturer's technical manual. The following is a checklist that is used to verifythat the type, the rating, and the operational characteristics of a switch are correct for theapplication based on Saudi Aramco and industry standards:

Verify that the switch meets the Saudi Aramco requirements that are shown in Figures13 and 14.

Verify that the switch frequency rating is correct for the application.

Verify that the switch rated maximum voltage is correct for the application:

- Rated continuous current at 60 Hz

- Rated load interrupting current

- Rated momentary, making, and one-second current

- Rated cable charging interrupting current

- Rated magnetizing interrupting current

Verify that the switch impulse withstand voltage (BIL) is correct for the application.

Verify that the switch operational characteristics will provide adequate protection forthe electrical equipment that is in the circuit with the switch (e.g., fuse rating). Switchrating information can be found on the switch nameplate or in the manufacturer'stechnical manual.




WORK AID 2: REFERENCES FOR EVALUATING MOTOR VARIABLE SPEEDDRIVE INSTALLATION AND TESTING

The information that is presented; has been assembled from SAES-P-116, 16-SAMSS-510, ANSIC37, GI-2.710, and related industry standards.

Figure 16 shows a Saudi Aramco Pre-Commissioning Form, P-001, Switches; High and MediumVoltage Air, Oil, and SF-6. P-001 contains a checklist and data tables for visual, mechanical, andelectrical inspections, as well as mechanical and electrical tests, of medium and high voltageswitches.




Figure 16: Saudi Aramco Pre-Commissioning form, P-001,Switches; High and Medium Voltage Air, Oil, and SF-6




Figure 16: Saudi Aramco Pre-Commissioning form, P-001,Switches; High and Medium Voltage Air, Oil, and SF-6 (Cont'd)




Information, Formulas, and Tables for Use in Evaluating the Results of InsulationResistance (Megger) Tests

The results of all commissioning megger tests that are performed must be documented on theappropriate Saudi Aramco pre-commissioning form. A short time (1 minute) megger test isperformed.

Figure 17 shows the recommended megger test voltages for various equipment voltage ratings.

Equipment RecommendedMegger

Voltage Rating Test Voltage

100 - 250 500

251 - 600 1000

601 - 2500 2500

5000 + 5000

Figure 17: Recommended Megger Test Voltages

Figure 18 provides bolt torque values for bus connections.

Bolt Size Tightening Torque#8 - 32 10 - 15 inch pounds#10 - 32 15 - 20 inch pounds1/4 x 20 5 - 7 foot pounds5/16 x 18 10 - 12 foot pounds3/8 x 16 18 - 20 foot pounds1/2 x 13 40 - 50 foot pounds

Figure 18:

commissioning switches, medium & high voltage

Documents

aramco requirements

technical material

visual inspection

vice president

additional information

contactfile reference

written permissionof

nameplate data