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9

Zone grading (or relay interlocking) is supported on the SIGMA-MD monitor relay. If voltage free, normally open (NO) 
contacts connected to the ZONE I/L input terminals are closed, the relay’s ground fault trip time delay is extended 
by 750 msec.

The SIGMA-MD monitor relay has a trip Inhibit input. If voltage free, normally open (NO) contacts connected to the 
INHIBIT input terminals are closed, the relay’s ground fault trip and NGR fault trip functions are inhibited.

Operation of the trip inhibit circuit will prevent the SIGMA-MD monitor 
relay from tripping on either an NGR fault or a ground fault. Care must 

be taken to ensure that the trip inhibit circuit is operated only for a 

short time to prevent injury or damage to the system’s transformer or 

circuits connected to the system’s transformer secondary.

WARNING

5. TRIP RELAY AND AUXILIARY FAULT RELAYS

The SIGMA-MD monitor relay has four output relays:

• The trip relay can be programmed for shunt (not failsafe) or undervoltage (failsafe) operation. The trip relay 
will trip on either an NGR fault or a ground fault.
• The NGR fault auxiliary relay can be used to give local (door/panel) or remote indication of an NGR fault.
• The ground fault auxiliary relay can be used to give local (door/panel) or remote indication of a ground fault.
• The SIGMA-MD health monitor relay can be used to indicate the health status of the relay. If the SIGMA-MD 
loses power or if the SIGMA-MD processor fails, this normally closed relay will open. The contacts will close 
when the power LED turns on and remain closed as long as the relay is operating correctly.

All relays are electrically held, i.e. when power is off, the relays are always in the de- energized state. The de-
energized state of the relay contacts is shown on the front panel of the SIGMA-MD monitor relay (with the exception 
of the SIGMA-MD health monitoring relay). Note that this is irrespective of the trip relay operating mode.

All relays can be in one of two states, idle or tripped. Whether the trip relay is energized or de-energized when in one 
of these states depends on the trip relay operating mode.

When the trip relay operating mode of the SIGMA-MD monitor relay is set for the shunt (non-failsafe) mode and no 
fault condition is present, the trip relay is Idle or de-energized. If a fault condition is detected and qualified, the trip 
relay is tripped or energized.

When the trip relay operating mode of SIGMA-MD monitor relay is set for the undervoltage (failsafe) mode and no 
fault condition is present, the trip relay is normally Idle or energized. The trip relay is tripped or de-energized if a fault 
condition is detected on the system. The failsafe mode of operation allows the SIGMA-MD monitor-MD relay to be 
configured such that the trip relay is de-energized and put into its tripped state when control power is off.

Refer to Table 1, trip relay operating mode setting for description of relay states when SIGMA-MD monitor relay is 
idle/not-tripped for the failsafe and non-failsafe operating modes.

Содержание SIGMA-MD

Страница 1: ...C EG42EM Instruction Manual December 2018 Previously C 455EM GROUND FAULT RELAY NEUTRAL GROUNDING RESISTOR SIGMA MD...

Страница 2: ...s 10 6 1 Start Up and Reset Indications 10 6 2 Power on Led Green 11 6 3 Ground Fault Led Red 11 6 4 NGR Fault Led Red 11 6 5 Zone Ground Led Red 12 7 Self Test 12 8 Relay Settings 13 8 1 Trip Relay O...

Страница 3: ...omer service and technical leadership We build on this foundation by investing in developing new products in electrical safety education including EFC scholarship program by actively participating in...

Страница 4: ...present Hazard of Electrical Shock Burn or Explosion All installation servicing and testing referred to in this manual must be performed by qualified personnel All power should be disconnected prior...

Страница 5: ...minal value When the ZSCS current is below 1 of the NGR let through current setting the SIGMA MD monitor relay simply monitors the NGR resistance for continuity i e whether the NGR is open or presents...

Страница 6: ...fast response is necessary as failure of the NGR implies that there is limited ground fault protection on the system It also ensures fast tripping when a transformer is energized and the resistor is...

Страница 7: ...necting the NGRS from the SIGMA MD monitor relay the R terminal of the NGRS should be disconnected BEFORE the Ground connection is removed from the G terminal of the SIGMA MD monitor relay The procedu...

Страница 8: ...e trip relay terminals the auxiliary fault relay terminals the external reset test and the G F meter terminals If door panel mounted or remote test and or reset controls are required connect momentary...

Страница 9: ...MD MONITOR RELAY AND NGR The SIGMA MD monitor relay has settings for the let through current ground fault trip current level and ground fault time delay These settings may be specified in the installa...

Страница 10: ...r if the SIGMA MD processor fails this normally closed relay will open The contacts will close when the power LED turns on and remain closed as long as the relay is operating correctly All relays are...

Страница 11: ...et flashing The trip relay auxiliary fault relays and associated LED will remain as such indefinitely regardless of whether a fault is present on the system and until the conditions which caused the t...

Страница 12: ...l be ON when the SIGMA MD monitor relay has detected and qualified a ground fault The RED GND FAULT LED will remain ON until the SIGMA MD monitor relay is manually reset even if the NGR fault conditio...

Страница 13: ...GMA MD monitor relay and no voltage applied to system transformer s primary winding Alternatively the system transformer s primary winding may be powered with the system transformer secondary isolated...

Страница 14: ...en control voltage is applied to the SIGMA MD monitor relay and the system is operating normally The trip relay is energized trip when the measured values of the ground fault current or NGR resistance...

Страница 15: ...A MD monitor relay will resume monitoring of the system and if a fault remains on the system will detect the fault and will re trip de energizing the trip relay 8 2 TRIP MEMORY SETTING The SIGMA MD mo...

Страница 16: ...ble and not higher than 20 when complying with this CSA Mine Safety Standard 8 5 SYSTEM FREQUENCY The SIGMA MD monitor relay has two settings for selecting the AC frequency of the system it monitoring...

Страница 17: ...is Idle Not Tripped Trip Relay is not energized Aux Fault Relays are not energized DOWN SIGMA MD Relay is Tripped Trip Relay is energized Aux Fault Relays are energized MODE DIP SWITCH SETTING Table 1...

Страница 18: ...U U D 1550 D U U U U 1650 U D D D D 1750 U D D D U 1850 U D D U D 1950 U D D U U 2050 U D U D D 2150 U D U D U 2250 U D U U D 2350 U D U U U 2450 U U D D D 2550 U U D D U 2650 U U D U D 2750 U U D U U...

Страница 19: ...y U UP D DOWN Table 4 Ground Fault Trip Current Level Settings SYSTEM FREQUENCY 60 50 Hz DIP SWITCH SETTING SYSTEM FREQUENCY 50 Hz UP SYSTEM FREQUENCY 60 Hz DOWN DIP switch 11 right hand array U UP D...

Страница 20: ...CS 550 U D U D I GARD TxA Type ZSCS 600 U D U U I GARD TxA Type ZSCS 650 U U D D I GARD TxA Type ZSCS 700 U U D U I GARD TxA Type ZSCS 750 U U U D I GARD TxA Type ZSCS 800 U U U U I GARD TxA Type ZSCS...

Страница 21: ...restored after a loss of control power the trip relay and auxiliary fault relays are returned to the state these relays had prior to the loss of control power The state of the trip relay and auxiliary...

Страница 22: ...s open or presents some resistance Trip Time Less than 60 seconds per CAN CSA M421 00 Typically 3 5 seconds 0 100 msec Up to 10 seconds under certain conditions Accuracy NGR Trip Resistance limits in...

Страница 23: ...the conductor on terminal G of the NGRS XX resistor sensor from ground and ensure the conductor is insulated 4 Disconnected the conductors between the X1 and X2 terminals of the TxA type ZSCS and the...

Страница 24: ...in less than 1s if ground fault current exceeds 20 of the prospective ground fault current 3 6 2 Neutral Grounding Devices A neutral grounding device shall be a continuously rated except when ground f...

Страница 25: ...24 Figure 2 Sigma MD Monitor Relay Detail A Typical NGRS Sensing Resistor Ngrs 6 Dual Voltage Model Shown Figure 3 Low Voltage NGRS Resistor Sensor...

Страница 26: ...25 Figure 5 NGRS 50 Figure 4 NGRS 25...

Страница 27: ...26 Figure 6 High Voltage NGRS Resistor Sensors...

Страница 28: ...www i gard com Phone 905 673 1553 Toll Free 1 888 737 4787 Fax 905 673 8472 support i gard com...

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