1

Earth Continuity RelaysElectrical safety for the mining industry.

Leaders in :

Voltage-Dip Proofing

Earth Continuity Monitoringsystemsswitching

ELECTRONIC ENGINEERS

2

ForewordSwitching Systems (Pty) Ltd was founded

in 1971 by F.V. Fischer. During the past threedecades we have established ourselves asSouth Africa's leading designers and manufac-turers of intrinsically safe earth continuity moni-tors and voltage-dip proofing systems.

All our products are manufactured to complywith various industry standards, and we arepermit holders of the SABS mark for intrinsicsafety, as well as being members of the SouthAfrican Flameproof Association. We have asophisticated research and developmentlaboratory for application to specific projects.

Switching Systems staff is a team dedicatedto providing product quality and service excel-lence. Our innovative spirit and continuousproduct improvement ensures the reliability ofour products.

We look forward to the opportunity of being ofservice to you.

F. V. FischerManaging Director

GCM-52-110 Earth Continuity Monitor

Pilot Wire Control Relays & Accessories

Switching Systems (Pty) LtdP O Box 33457, Jeppestown, 2043South AfricaTel: +27 (0)11 624 3317Fax: +27 (0)11 624 2382e-mail: info@switchingsystems.co.za

3

IntroductionEarth leakage relays perform two main

functions on mining installations: to protectmachinery from damage and to make the in-stallation safer for personnel. In the typicaldistribution circuit shown in Fig 1, an earthleakage relay provides protection against leak-age to earth and earth faults. The principle ofthis method is that all the current flowing to theload must return from the load. If current leaksto the frame of the motor and returns via theearth bond back to the star point of the supplytransformer then this difference is detected bythe earth leakage relay which triggers thebreaker, thus disconnecting the load.

It becomes apparent that the earthingmust be solid and reliable for electrical installa-tions to be safe. For this reason, machinery isearthed via the supply cable, using either acopper conductor of the cable or the armour.The ground on which the machinery stands isnormally not considered a reliable earth. Me-chanical damage to the earth bond, corrosionof the armour or bad workmanship may resultin a high resistance point in the earth return. Ifan earth fault occurs, voltage will be developedacross the high resistance region. This voltageposes a potential hazard to any personnel whomay be exposed to it. Depending on the resis-tance value, the current flowing and the reactiontime of the earth leakage relay, this could befatal. It is obvious that continuous monitoring ofthe earth bond is imperative if safety standardsare to be maintained.

SWITCHING SYSTEMS' range ofEARTH CONTINUITY RELAYS provides acost effective solution to the problem.

Fig 1A typical distribution circuit

I>I>I>

Supply Transformer

K1

EarthLeakage

Q1

Breaker

BusBars

NeutralEarthingResistor

LE

Ear

th

Load

Cable

ContactorwithOverload

4

Theory of OperationTo continuously monitor the resistance

of the earth bond, an electrical measuringsignal is fed into the earth conductor via aseparate pilot wire. To cater for the possibility ofa short between this pilot and the earth, aremote module must be employed.

A loop now exists, consisting of the pilotwire, the remote module and the earth wire inthe cable. An intrinsically safe signal is injectedinto the loop and, by interpreting the voltageand the current flowing, the resistance can bemonitored: see Fig 2. The energy level of anintrinsically safe signal is so low that dangerousgases like hydrogen or methane cannot beignited by it.

Depending on factors such as the lengthof the supply cable, the nature of the load,variable speed drives or very heavy loads, andthe location of the installation, [near a pipelinewith cathodic protection or a DC railway line], arange of noise signals can be induced orinjected into the loop: the signals can vary fromhigh frequency generated by thyristor switching,to 50Hz and DC. Noise signals can have anamplitude of up to 100V. The relatively lowlevel of the intrinsically safe measuring signaland the high electrical noise necessitated thedevelopment of specialised measuring circuitry.

Fig 2Pilot Wire Control Relay & 2-Wire Module

provide continuity sensing only

I>I>I>

Green

Bla

ckB

lack

BlueBlue

Gre

enP

ilot R

elay

Yellow

Brown

Red

Rem

ote

Mod

ule

SupplyTransformer

Control

Voltage

Q1-

1

5A

K1

Ext

erna

lTr

ip

K1-1

Sta

rtS

top

Load

Ear

th

Pilo

tCable

K1

ContactorWithOverload

EarthLeakage

Q1

Breaker

BusBars

NeutralEarthingResistor

LE

Purple

Yellow

5

Product DescriptionSWITCHING SYSTEMS' Earth

Continuity Monitors are grouped into twocategories:-

PILOT WIRE CONTROL RELAYS, pre-fixed GBP, MP & MSR.These relays offer simple and cost effectivesolutions. They have remote stop/startcapability. The maximum resistance level ispermanently set at 22 for GBP/MP relays, andat 100 for MSR Relays. They are used prima-rily underground with short cables and mediumpower loads.

Three generations of relays are available:• The first, MSR8, is not intrinsically safe.• The second, MSR9 & GBP4, is intrinsicallysafe, and is suitable for environments wherelimited electrical noise is present.• The third, MP130, provides for noise immunityof up 12Vin full operation mode & from 12 to50V in restricted mode. These relays can beused as direct replacements for older modelsand they are the preferred products for all newapplications.

EARTH CONTINUITY RELAYS,prefixed GCM.

This relay is micro-processor controlled andcan withstand high induced AC voltages andinjected DC voltages. The loop resistance isconstantly indicated on a 7 segment LCDdisplay. The trip level can be set using therotary switches on the front panel. Fault condi-tions such as open circuit, short circuit andhigh-resistance are displayed. A separate in-terface module provides a 4 to 20mA output forremote monitoring. The use of this modulerequires factory modification of the earth conti-nuity relay. These relays are mainly used forhigh voltage reticulation trailing cables on dra-glines and drills. Fig 3

Pilot Wire Control Relay with 3-Wire Moduleprovides continuity sensing & remote control

I>I>I>

Green

Bla

ck

Bla

ck

Blue

RemoteModule

K1-

2

Yellow

Gre

en

Blue

Pilo

t Rel

ay

RedPurple

YellowBrown

SupplyTransformer

Sta

rt

Sto

p

Control

Voltage

Q1-

1

5A

K1

K1

EarthLeakage

Q1

Breaker

BusBars

NeutralEarthingResistor

LE

Ear

th

Pilo

t

Load

ContactorwithOverload

Cable

Ext

erna

l Trip

BrownMainEarth

6

All Pilot Wire Control Systemsare wired in a similar way and consist of twoparts:-

The RELAY is normally situatedat the load centre and controls a contactor orthe trip coil of a circuit breaker. It is housed in anepoxy filled plastic box and is connected viaMolex plugs. Physical dimensions of the relayare shown inFig 4.

The REMOTE MODULE, ofwhich three different types are available:-

• A 2-wire Module used for loop resistancesensing only which consists of a resistor and adiode as shown in Fig 5.

• A 3-wire Module used for loop wire sensingand remote control. External Start and Stopbuttons must be added to control the remotecontactor, refer to Fig 6. Physical dimensionsof the 2-wire and 3-wire modules are identicaland are shown in Fig 7.

• A Pushbutton Station consisting of a 3-wiremodule and two pushbuttons cast together inepoxy. This hermetically seals the pushbuttoncontacts, making this module highly reliable industy environments. Physical dimensions areshown in Fig 8.

The system wiring diagram,showing the pilot wire control relay connectedas an earth loop monitor without remote control,appears on Page 4, Fig 2; a 2-wire module isrequired and the feedback contact from K1 isnot used. Fig 3, Page 5 shows a system whichuses a 3-wire module to provide earth loopmonitoring and remote control facilities.

Common Specificationsfor Pilot Wire Control Relays

Fig 4Dimensions of relays (in mm)

Fig 63-WireRemote Module Connection Diagram

Fig 52-Wire Remote Module Connection Diagram

Green

Earth

Black

Pilot

Green

Earth

Brown

Black

Start

Stop

Pilot

MP-130-ni Pilot Wire Control Relay

7

for Pilot Wire Control Relays

Common Specifications

1745

Ø6

Fig 7Dimensions of Remote Module (in mm)

Fig 8Dimensions of Pushbutton Station (in mm)

MSR9-ni Pilot Wire Control Relay

Pushbutton Station

2-wire & 3-wire Modules

GBP-4-ni Pilot Wire Control Relay

8

Control voltage : 110Vac +20% -30%220Vac +20% -30%525Vac +20% -30%

Relay burden : 10VA

Output contact : One potential free C/O rated at 5A 525VacTwo potential free C/O rated at 5A 250Vac

Earth loop detection : 100 ± 20%22 ± 20%

Line-to-pilot <30 sec on 2,5A restricted earth systemsfault withstand time : <2 sec on 2,5A restricted earth systems

Max ambient temp : Relays 45C; Remote Modules 120C

Classification : NoneSABS Intrinsically safe[Ex ib] I/IIc I.A. No. SABS MS/03-482x

Compliance standard : Complies with requirements of the A.A.C.;Specification 540/1Issue 3

Complies with requirements of the BritishStandards Institute: BS3101; 1986Complies with requirements of the BritishStandards Institute: P130

Suitable for noise levels : Below 2VacBelow 12Vac, restricted operation >12V-50Vac

Connections :

✓ ✓✓ ✓

✓ ✓ ✓ ✓

✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

✓ ✓ ✓ ✓ ✓ ✓✓ ✓

✓ ✓✓ ✓ ✓ ✓ ✓ ✓

✓ ✓ ✓✓ ✓ ✓ ✓ ✓

✓ ✓ ✓ ✓ ✓ ✓ ✓ ✓

✓

✓ ✓ ✓ ✓ ✓ ✓ ✓

✓ ✓

✓ ✓ ✓

✓ ✓ ✓

✓✓ ✓ ✓ ✓ ✓ ✓ ✓

✓

Specifications

MS

R 8

MS

R 9

-ni

GB

P-4

-ni-

110

GB

P-4

-ni-

220

GB

P-4

-ni-

525

MP

130-

ni-

110

MP

130-

ni-

220

MP

130-

ni-

525

for Pilot Wire Control Relays

Parameter

YEL

GRNBLKYEL

RED9A

BLU8A

BLU7A

PUR6A

BRN5A4A

3A2A1A1. Yellow : Feedback 6. Purple : Common-12. Black : Pilot 7. Blue : Supply3. Green : Earth 8. Blue : Supply4. Yellow : Feedback 9. Red : N/O-15. Brown : N/C-1

9

✓ ✓ ✓ ✓ ✓

✓ ✓

✓✓ ✓

✓ ✓✓ ✓✓

✓✓

✓✓

✓✓ ✓ ✓ ✓ ✓ ✓✓ ✓ ✓ ✓ ✓ ✓✓ ✓ ✓ ✓ ✓ ✓✓ ✓

✓ ✓ ✓ ✓

✓✓

✓

MS

R 8

MS

R 9

-ni

GB

P-4

-ni-

110

GB

P-4

-ni-

220

GB

P-4

-ni-

525

MP

130-

ni-

110

MP

130-

ni-

220

MP

130-

ni-

525

Specificationsfor Pilot Wire Control Relays

Parameter

YELYEL BLK

GRN

1B2B3B4B

RED9A

BLU8A

BLU7A

PUR6A

BRN5A4A

3A2A1A

Connections :

Ordering :Stock No Description

5001-001 MSR8 Relay5001-003 MSR8/9 Pushbutton Station

5001-004 MSR8/9 2-Wire Blue Module5001-005 MSR8/9 3-Wire Blue Module5001-002 MSR8 Connection Leads5001-007 MSR9-ni-525 Relay5001-010 MSR9 Connection Leads5001-013 GBP-4-ni-110 Grey Pilot Wire Relay5001-015 GBP-4-ni-220 Red Pilot Wire Relay5001-017 GBP-4-ni-525 Blue Pilot Wire Relay5001-019 GBP/MP Pushbutton Station5001-020 GBP/MP 2-Wire Buff Module5001-021 GBP/MP 3-Wire Buff Module5001-018 GBP-4/MP130-110 Connection Leads5001-010 GBP-4/MP130-220/525 Connection Leads

5001-023 MP130-ni-110 Relay5001-025 MP130-ni-220 Relay5001-027 MP130-ni-525 Relay

ORAGRYWHT

YELYEL BLK

GRN

1B2B3B4B

RED9A

BLU8A

BLU7A

PUR6A

BRN5A4A

3A2A1A

1A. to 4A. : Not Used 1B. Green : Earth5A. Brown : N/C-1 2B. Black : Pilot6A. Purple : Common-1 3B. Yellow : Feedback7A. Blue : Supply 4B. Yellow : Feedback8A. Blue : Supply9A. Red : N/O-1

1A. White : Common-2 1B. Green : Earth2A. Grey : N/O-2 2B. Black : Pilot3A. Orange: N/C-2 3B. Yellow : Feedback4A. - : Not Used 4B. Yellow : Feedback5A. Brown : N/C-16A. Purple : Common-17A. Blue : Supply8A. Blue : Supply9A. Red : N/O-1

10

Specificationsfor Earth Continuity Monitor

The GCM-52-110 is mounted in a com-pact plastic case and is connected via twoMolex plugs. A typical application circuit isshown in Fig 9.

The external connections consist of twoterminals for the supply voltage, three termi-nals each for the two potential free change overcontacts; plug A and one each for the pilot andearth connections; plug B. The truth table forthe operation of the two changeover contacts isshown in Fig 10. This configuration was chosento provide a “no power on unit” indication. Thedimensions and connection diagrams areshown in Figs 12 & 13 respectively.

The remote module consists of a 100,1% 30 watt calibrated resistor, terminated witha M12 and M8 brass bolt, for connection toEarth and Pilot respectively. For physical di-mensions see Fig 14 on page 12.

The protection filter prevents damage tothe monitor due to phase to earth and phase topilot faults. The monitor filter can continuouslywithstand faults on restricted neutral systemsup to 300A without damage to the filter ormonitor. It is recommended that a protectionfilter should be purchased together with a newGCM-52 monitor and consideration should begiven to installing a protection filter to to protectthe monitor in existing installations. Electricaland me-chanical specifications appear onpage 11.

The GCM-52 replaces the older modelGCM-110 & the GCM-51. An adapter plate isavailable which allows the GCM-52 to bemounted in the GCM-110 enclosure, aphotograph of the GCM-52 mounted on theadapter plate appears on page 12.

Fig 9Typical Earth Continuity Monitor application

I>I>I>

Pilo

t M8

Earth M12

Rem

ote

Mod

ule

Earth

Con

tinui

ty M

onito

r

SupplyTransformer

LE

Q1

NeutralEarthingResistor

BusBars

EarthLeakage

Breaker

Control

Voltage

Load

Ear

th

Pilo

tCable

Pro

tect

ion

Filt

er

11

Specificationsfor Earth Continuity Monitor and Protection Filter

MODEL GCM-52-110Control voltage: 110V AC: Sinusoidal 50HzVoltage variation: ± 15%Relay burden: 15VAOperational accuracy: 0,5Measurement limit: 90Resolution: 0,1Open circuit fault: 2kOpen circuitresponse time: 50msShort circuitresponse time: ± 25sHigh resistanceresponse time: ± 25sOutput contact: 2 Potential free changeover

contacts. 5A 220V ACContact arrangement: See Fig 10Mounting: Surface mounting enclosure

See Fig 12Connections: Prewired Molex plug/socket

with colour-coded conductorharness.(wirelength 1m) :See Fig 13

Compliance standard: SABS Intrinsically safe,Group 1, 2a, 2b, 2c.Temperature Class T1 to T5.

MODEL GCM-PF1 Protection FilterCurrent rating 39A continuousNon repeditive peak 580AI2t 1400A2 secSurge Voltage 5Kv at 5 JoulesInsulation voltage 2,5KvLine resistance 0,4 maxClamping voltage 55v peakWeight 1Kg

OrderingStock No Description5001-050 GCM Remote Module5001-070 GCM-52 Earth Continuity Monitor5001-053 GCM-52 Connection Leads5001-058 GCM-PF1 Protection Filter

Fig 10Operation of Relay contacts

PILOT IRRELEVANT PILOT HEALTHY PILOT UNHEALTHY

3A 3A 3A1A 1A 1A2A 2A 2AGCM-51-110

5A 5A 5A6A 6A 6A9A 9A 9AGCM-51-110

Relay"B"

Relay"A"

Condition Supply OnSupply OnSupply Off

De-energised

Energised

EnergisedDe-energised

De-energisedDe-energised

Fig 11Dimensions of GCM-PF1 Protection Filter(in mm)

GCM-PF1 Protection Filter

systemsswitching

ELECTRONIC ENGINEERS

GCM Earth Continuity MonitorProtection Filter

Model : GCM-PF1

110

(4.3

3)

150 (5.90)

140 (5.50)

131.

5(5

.18)

5mm

Ø

1 2 4

Pilot(Line)

Earth Pilot(Monitor)

3

12

Specificationsfor Earth Continuity Monitor

GCM Remote Module

Fig 13Connections for GCM-52-110

Fig 14Dimensions of Remote Module (in mm)

Fig 12Dimensions of GCM-52 Enclosure (in mm)

GCM-52-110 Earth Continuity Monitor

BLK GRN

1B2B3B4B

RED9A

BLU8A

BLU7A

PUR6A

BRN5A4A

ORA3A

GRY2A

WHT1A

GCM-52 mounted on Adapter Plate

1A. White : Common-B2A. Grey : N/O-B3A. Orange : N/C-B4A. - : Not Used5A. Brown : N/C-A6A. Purple : Common-A7A. Blue : Supply8A. Blue : Supply9A. Red : N/O-A1B. Green : Earth2B. Black : Pilot3B. - : Not Used4B. - : Not Used

218

Connection lead colour codes (length = 2M)

53

144

2B 8A

138

7A1A 5A1B

6872

9A3A2A 6A

5A Brown6A Purple Relay "A"9A Red

3A Orange1A White Relay "B"2A Grey

7A Blue 110V Supply8A Blue 110V Supply

1B Green Earth2B Black Pilot

Panel cutout size :-69mm x 139mm

Socket "A"Socket "B"Sockets "A" & "B" exitenclosure via flying leads100mm long.

13

AccessoriesPHASE SEQUENCE RELAY

The RPF550/1100V Phase SequenceRelay drops the power supply contactor if thephase sequence of the supply is incorrect. Thedirection of rotation is a vital factor in the caseof drives for pumps, fans, compressors andconveyors. In certain circumstances, particu-larly where mobile equipment is employed, it isadvisable to monitor the direction of rotationand to disconnect the power source if the driveruns in the reverse direction. The unit is usuallysituated at the load centre and is wired inconjunction with a pilot wire relay for contactorcontrol, see Fig 15; for physical dimensionssee Fig 16.

Specifications :

Input voltage : 550 or 1100Vac 3 phaseDetection : Reverse phase & phase failureOutput contact : One potential free C/O rated at

3A 250Vac

Ordering :

Stock No Description5002-001 RPF550/1100

Fig 16Dimensions of RPF Relay (in mm)

for Earth Continuity Monitor

Fig 15Connection of Phase Sequence Relay

I>I>I>

RP

F 55

0/11

00V

Bla

ck

Bla

ck

Green

Blue

Sto

p

Sta

rt

RemoteModule

A1B2C3

Yellow

Gre

en

Blue

Pilo

t Rre

lay

RedPurple

YellowBrown

SupplyTransformer

Q1-

1

K1-

2

ControlVoltage

5A

K1

ContactorwithOverload

K1

EarthLeakage

Q1

Breaker

BusBars

NeutralEarthingResistor

LE

Ear

th

Pilo

t

Load

Cable

Ext

erna

l Trip

Brown

14

Accessoriesfor Earth Continuity Monitors

EARTH FAULT LOCKOUT RELAYThe EFLR-1100-110 Earth Fault Lock-

out Relay prevents the power supply contactorfrom closing if an earth fault is present on thecable. This ensures that only healthy circuitsare energised, eliminating damage to equip-ment and protecting personnel from potentialshock hazard.The unit is normally situated atthe load centre and is used in conjunction witha pilot wire relay for contactor control: Fig 17shows a typical application circuit. Physicaldimensions of the relay are shown on page 6,Fig 4. The relay is connected via a 9 pin Molexplug & terminal block: the connection tablesappear in Fig 18 below.

Fig 18Connections for EFLR-1100-110

Fig 17Connection of Earth Fault Lockout Relay

Specifications :

Control voltage : 110Vac ± 15%Relay burden : 10VAOutput contact : One potential free C/O

rated at 5A 220VacEarth fault detection : 10k Insulation resistanceSystem voltage : 1100Vac 3 phaseMax amb temp : 65C

Ordering :

Stock No Description5002-035 EFLR-1100-110 Connection leads5002-030 EFLR-1100-110 Earth Fault Lockout Relay

1. No connection2. No connection3. No connection4. No connection5. Brown : N/C6. Purple : Common7. Blue : Supply 110V8. Blue : Supply 110V9. Red : N/O

Screw Terminal Connector B1. Phase 1 : 2. Phase 2 : 3. Phase 3 : 4. Earth

NC

NCNC

RED9A

BLU8A

BLU7A

PUR6A

BRN5A4A

3A2A1ANC

Plug A

I>I>I>

Green

Bla

ck

Bla

ck

Blue

RemoteModule

Yellow

Gre

en

Blue

Pilo

t Rel

ay

RedPurple

YellowBrown

8A7A

1B2B3B4B

5A

6A

9A EFLR

-110

0

SupplyTransformer

Q1-

1

K1-

2S

tart

Sto

p

Control

Voltage

5A

K1

ControlVoltage

K1

EarthLeakage

Q1

Breaker

BusBars

NeutralEarthingResistor

LE

Ear

th

Pilo

t

Load

Cable

ContactorwithOverload

Ext

erna

l Trip

Brown

15

RESTRICTED EARTH FAULT SYSTEMNeutral earthing resistors are used to

limit the high currents that can flow in powertransformers under earth fault conitions.

The NEUTRAL EARTHING RESISTORMONITOR is designed to continuously monitorthe integrity of the system neutral earthingresistor. Fault conditions trigger visual andaudible alarms. Earth fault detection isincorporated as a secondary feature. Themonitor operates on a fail safe principle and isdesigned to withstand earth fault voltagescontinuously without damage. Push buttonsare provided to simulate a faulty neutral earthingresistor and an earth fault so that the operationof the monitor can be checked at any time.

Each NEUTRAL EARTHING RESISTORMONITOR is custom designed to work with ourcustomers' system, for this reason no detailedspecifications are given here. A typicalconnection diagram is shown in Fig 19 and ageneral panel layout in Fig 20. Customersshould contact our sales department to discusstheir system requirements.

Fig 19Connection of Neutral Earthing Resistor Monitor

Fig 20Typical Monitor Front Panel Layout

SupplyTransformer

NeutralEarthingResistor

Neutral EarthResistor Monitor

YellowPhase

RedPhase

2

3

14 Neutral

Earth

Specificationsfor Neutral Earthing Resistor Monitor

16

Earth Continuity RelaysElectrical safety for the mining industry.

systemsswitching

ELECTRONIC ENGINEERS

PO Box 33457, Jeppestown, 2043,

Republic of South Africa.

Telephone : +27 (0)11 624 3317

Fax : +27 (0)11 624 2382

e-mail: info@switchingsystems.co.za

Doc Ref. 3401-005 Rev 1.1 : 12th January 2006 : LPW