measurement techniques svxhwm

Operating Instructions

3-32 VECTRON SVX Technical Reference Guide

MEASUREMENT TECHNIQUESThe VECTRON meter samples small portions of the input voltages from the voltage and current sensing elements. Each sample is converted into a binary number and then used by the microcontroller to derive the billing values. This phase selection, sampling, and measurement process is described in the following sections.

SamplingDuring one cycle of the power source, the VECTRON meter takes 8 samples for each of the voltages and the currents on each of the phases. The phase A voltage is sampled first, followed by the phase A current, and then the phase B voltage, and so on. These groups of 6 samples are therefore spaced 2.08 milliseconds apart if the register is operating on 60 Hz, or 2.5 milliseconds if the register is operating on 50 Hz (see Figure 3.9).

Figure 3.9 Sampling

Before this procedure is repeated for the next cycle, a delay is added so that the relative position of the next group of 8 samples on the waveform is shifted in time with respect to the samples taken during the previous cycle. This ensures that each group of samples is not taken at an identical point during the cycling of the signal. This technique, called sample migration, helps the VECTRON meter maintain metering accuracy under harmonic distortion conditions (see Figure 3.10).

Each group includes a sample of V and I on each of the three phases.

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VECTRON SVX Technical Reference Guide 3-33

Figure 3.10 Sample Migration

After 60 cycles, the microcontroller has a complete picture of the waveform as if it has been sampled 481 times (480 + 1 because of the migration) in one cycle (see Figure 3.11).

The line synchronization signal is used to derive the time base for the sampling. It dynamically tunes the sample interval to ensure that there are always the correct number of samples regardless of the line frequency (481 samples for 60 Hz, 401 samples for 50 Hz).

Figure 3.11 Waveform Sampling

Voltage and Current MeasurementsDuring the sampling process, the voltage and current values from each phase are squared and stored in their respective accumulators.

At the end of the 60th cycle, each accumulator contains the sums of the square of the voltages and currents for each phase (see Figure 3.12). The contents of these accumulators are passed to the consumption routing where they are

Two consecutivecycles have samples that are 34 microseconds or 0.75° apart.

One group of samples on all Vs and 1s.

After 60 cycles, the entire waveform has been sampled at 34 intervals.



averaged (divided by 481) and the square root is taken, yielding the RMS voltage and RMS current for each phase. The accumulators are reset before the first of the next set of 481 samples is taken.

Figure 3.12 Accumulator

Instantaneous Voltage and Instantaneous Current

Each of the per phase voltage and current values is displayed in the Toolbox Mode. The value displayed is the RMS value calculated for the previous 60 cycles.

Watthour MeasurementWatthours are measured by multiplying the instantaneous value of the voltage on each phase with the instantaneous value of the current on the same phase (see Figure 3.12).

The resulting values are added to running accumulators. After the completion of 481 samples (one second for 60 Hz supply or 1.2 seconds for 50 Hz supply), the reading in this accumulator is passed to the consumption routing where it is averaged (divided by 481), scaled, corrected, divided by 3600, and then added to the main registers.

The VECTRON meter can be programmed to register watthours either in the delivered quadrants only, or in the delivered and received quadrants.

When delivered watthours only are measured, any negative watthour values are ignored. This has the same effect as a detent mechanism on an induction watthour meter.

When delivered and received watthours are measured, any negative watthour values are made positive and added to the watthour register.

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Varh Measurement (Extended Function Version)Varhours are measured by multiplying the instantaneous value of the first available voltage sample on one phase with the instantaneous value of the third available current sample of the same phase (Figure 3.12). Since voltage samples are continually stored in a three location, last in, first out (LIFO), shift register, the first available voltage sample from the register is the one taken three samples (90° phaseshift) previous to the instant of the request for a Varh reading.

Each Varh measurement is added to a running accumulator. After the completion of 481 samples (approximately one second for 60 Hz supply or 1.2 seconds for 50 Hz supply), the reading of the accumulator is passed to the consumption routine where it is averaged, scaled, corrected, and added to the main registers.

VAh Measurements (Extended Function Version)The VECTRON meter measures RMS volt-amperes using arithmetic phase summation. This method ensures that the resulting VAh value contains as much of the harmonic information as possible.

Volt-ampere values are calculated by multiplying the RMS voltage value with the coincident RMS current value (see Figure 3.12) using the following formulas:

VA = VRMS

x IRMS

where

VRMS

= and IRMS

=

where N is the number of samples per second.

The voltage and current values from each phase are squared and stored in their respective accumulators. At the end of the 60th supply cycle, each accumulator contains the sums of the square of the voltages or currents for each phase. The contents of these accumulators are passed to the consumption routine where they are averaged (divided by 481) and the square root is taken, yielding the RMS voltage and RMS current for each phase.

Every second, the RMS voltage and the RMS current for each phase are multiplied together to establish a VA-second value for each phase. These values are scaled and corrected.

The total VA hour value is calculated by adding the VA-second quantities for each phase and dividing the total by 3600. This value is added to the appropriate register.

If apparent energy is selected as the extended function, the VECTRON can be programmed to calculate VA either vectorially or arithmetically on delta services. The vectorial calculation uses the following formula:

VA =

1N VN

2

∆ N→∑ 1

N I

N2

∆ N→∑

Watts2 Vars2+

Notes:



General Information


Cover options include:

• Without demand reset

• Keylock demand reset

• Battery access door with demand reset

• Battery access door without demand reset

• Battery access door with keylock demand reset

Outputs (Optional)Two optional outputs are available on all versions of VECTRON meters:

• One or two mercury-wetted relays

• One form A solid-state contact closure

Two additional optional outputs are available on all versions of the VECTRON SVX meters:

• One or two Form C solid-state contact closures

• AMR interface

Each form C solid-state contact can be used as a pulse initiator output (KYZ), demand threshold output, end of interval output, load control output (independent output), customer alert output, or diagnostic condition alert output.

The AMR output uses solid-state technology to connect directly to the T-3000 MIU (Meter Interface Unit), which is part of the inbound telecommunications system.

Communication Boards (Optional)Following are brief descriptions of optional boards, either communication or output, for the VECTRON meter. The meter can support only one board at a time. Because of this, the modem, RS-232, and RS-485 are available in solid-state outputs for situations where both a communication and an output board are required. The R300V does not offer solid-state outputs. If you require a board with solid-state output, it must be specified at the time of order.

Modem

An optional modem is available on all versions of the VECTRON SVX meters. The basic modem includes:

• Parallel off-hook detect (RJ-11 connector)

The load control and customer alert outputs are only available with the TOU, mass memory, or the ex-tended function versions of the VECTRON meter.

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• Phone home on event

• Calling windows

• Phone line sharing capability

• 300/1200/2400 baud support with autobaud detection

All VECTRON SVX modems have the capability of initiating a phone call on a schedule. Additionally, the modem can initiate a phone call on an event. Events include fatal or non-fatal errors, per phase current or potential loss, diagnostic error, power restoration, and exceeded demand threshold.

Optional features available on the VECTRON SVX modem include:

• Serial off-hook detect (RJ-31 connector)

• Phone home during outage

• Solid-state outputs

R300V

The R300V is an option board that allows energy and maximum demand values to be transmitted from the VECTRON via radio frequency. Features include:

• Broadcast energy only for demand meters

• Broadcast energy and demand for TOU meters

• Tamper detection

• All components housed within meter

RS-232 and RS-485

The RS-232 and RS-485 boards offer serial communications with the VECTRON meter. Both boards support point-to-point communications and multi-drop communications using SCS protocol. Features include:

• 12 position DIP switch for configuration options

• 2 KYZ outputs with 1 LC available

• Addressable (up to 256 address available)

• Signal conversion

• Hand shaking

• Isolation

• Baud rates configurable (1200, 2400, 4800, 9600)

• DB9-F DTE connector on RS-232

• RJ11 connector on RS-485

General Information


DISPLAY ITEMSAll VECTRON meters can display a maximum of 32 Normal, 32 Alternate, and 10 Test items, up to a total count of no more than 48 items. The display items and sequence of display, along with any desired annunciators or ID code number, are selected during program setup, a feature of the PC-PRO+ software.

Table 1.1 lists, in alphabetical order, items programmable for display in the modes indicated. Detailed information about these display items is given in the PC-PRO+ Software User’s Manual.

Table 1.1 VECTRON Display Modes

Display Item Normal Alt. Test Toolbox

Continuous Cumulative kVA total (E rate only)* X X

Continuous Cumulative kvar lag (E rate only)* X X

Continuous Cumulative kW (E rate only)* X X

Continuous Cumulative kVA lag (E rate only)* X X

Cumulative kVA lag (E rate only)* X X

Cumulative kVA total (E rate only)* X X

Cumulative kvar lag (E rate only)* X X

Cumulative kW (E rate only) X X

Current Date (TOU only) X X

Current Time (TOU only) X X

Date Max Demand (TOU only) X X

Day of Week (TOU only) X X

Days Since Last Reset X X

Demand Threshold Value X X

Diagnostic Counters (d1, d2, d3, d4, d5) X

Display Duration X X

Error Codes X X

Firmware Revision # (Back End) X X

Firmware Revision # (Front End) X X

Instantaneous Amps (per phase) X

Instantaneous kVA lag* X X X

Instantaneous kVA total* X X X

Instantaneous kvar lag* X X X

Instantaneous kW X X X

* Indicates items available for display with the extended function version only. The energy and demand quantities which show up in the display item list will vary depending on the extended registers selected for that particular configuration, such as vars or VA.

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Instantaneous Volts (per phase) X

kVAh lag* X X X

kvarh lag* X X X

kvarh lead* X X X

kWh X X X

KYZ pulse weight #1 X X

KYZ pulse weight #2 X X

Last Season Billing Values (TOU only) X X

Maximum kVA lag* X X X

Maximum kVA total* X X X

Maximum kvar lag* X X X

Maximum kW X X X

Meter ID 1 (9 digits) X X

Meter ID 2 (9 digits) X X

Meter Kh X X X

Normal Mode Subinterval Length X X

Number of Demand Resets X X

Number of Power Outages X X

Per Phase Current Angle X

Per Phase Voltage Angle X

Present Interval Input Pulse Count X

Present Interval kVA lag* X X X

Present Interval kVA total* X X X

Present interval kW X X X

Previous Interval Input Pulse Count X

Previous kvar* X X

Previous kVA* X X

Previous kW X X

Program ID Number (3 digits) X X

Segment Test X X

Software Revision X X

* Indicates items available for display with the extended function version only. The energy and demand quantities which show up in the display item list will vary depending on the extended registers selected for that particular configuration, such as vars or VA.



General Information


* Indicates items available for display with the extended function version only. The energy and demand quantities which show up in the display item list will vary depending on the extended registers selected for that particu-lar configuration, such as vars or VA.

Specifications

Electrical

Test Maximum kW X

Test Mode Number of Subintervals X X

Test Mode Subinterval Length X X

Time and Date Last Programmed (TOU only) X X

Time and Date of Last Reset (TOU only) X X

Time Max Demand (TOU only) X X

Time on Battery Carryover (TOU only) X X

Time Remaining Before Test Mode Timeout X

Time Remaining in Subinterval X X X

TOU Program Expiration Date (TOU only) X X

TOU Rate Schedule ID Number (TOU only) X X

Transformer Factor X X

User Defined Fields (up to three 9-digit fields) X X



Voltage Ranges (before SVX): 60 Hz range: (Nominal) 60 Hz range: (Actual)

1 120-277 volts 96-332 volts

2 240-480 volts 192-552 volts

3 100-115 volts 80-132 volts

4 57.7-63.5 volts 46-76 volts

Voltage Ranges SVX: 120-480 volts 96-528 volts

Frequency: 50 Hz or 60 Hz

Operating Range: ± 3 Hz

TOU/Extended Function Battery

Voltage: 3.6 V nominal

Operating Range: 3.4 V - 3.8 V

Carryover:

TOU 365 days minimum

TOU/Extended Function with mass memory 300 days minimum

Surge Suppression IEEE C62.41 - 1980

measurement techniques svxhwm

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