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MV Switchgear Relay Coordination

This document discusses relay coordination between the incomer and outgoing feeders of MV and LV switchgear. It provides calculations of operating times for overcurrent protection relays on a motor feeder, transformer feeder, and outgoing feeders of LV switchgear. Minimum time multiplier settings are determined to ensure discrimination and coordination between protection devices during fault conditions.

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Noli Oteba
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1K views8 pages

MV Switchgear Relay Coordination

This document discusses relay coordination between the incomer and outgoing feeders of MV and LV switchgear. It provides calculations of operating times for overcurrent protection relays on a motor feeder, transformer feeder, and outgoing feeders of LV switchgear. Minimum time multiplier settings are determined to ensure discrimination and coordination between protection devices during fault conditions.

Uploaded by

Noli Oteba
Copyright
© Attribution Non-Commercial (BY-NC)
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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RELAY COORDINATION BETWEEN INCOMER & OUTGOING FEEDERS OF MV SWITCHGEAR

CTR 2500/1

I/C

CTR 700/1

CTR 250/1

CTR 2500/1

CTR 1250/1

4500KW

2500KVA

2500 A

1250 A

I]

Between Incomer and Motor Feeder FAULT TYPE: SHORT CIRCUIT Motor Rating Motor rated voltage Motor full load current CT Ratio (CTR) CT Secondary current

4500 KW 6.6 KV 454.2 700/1 0.65

Calculation of Operating time of over current protection of Motor Feeder Current Setting in % (PS) Current Setting (I>) (CTR X PS) Fault Current considered (Amps) (I) Operating time calculated as follows

2.0 1400.00 25000

1 >

+ K
IEC Very inverse (A) (B) 13.5 0

1 >

Selected Characteristic Time/current curve group Very inverse C K (TMS)

1 0.7

Operating time of Over current protection,t (sec)


II Calculation of required TMS for Incomer Feeder Fault current considered (A) Current Setting in % (PS) Current Setting (I>)

0.5606
25000 100% 2500

Operating time calculated as follows

1 >

+ K
IEC Very inverse (A) (B) 13.5 0

1 >

#REF!

Selected Characteristic Time/current curve group Very inverse C K (TMS)

1 0.92

Operating time of Over current protection,t (sec)

1.38
0.529 0.92

Minimum TMS for discrimination Selected TMS considering that TIE between unit boards are closed

I]

Between Incomer and Transformer Feeder FAULT TYPE: SHORT CIRCUIT Transformer Rating Transformer rated voltage Transformer full load current CT Ratio (CTR) CT Secondary current

2500KVA 6.6 KV / 433V 218.69 250/1 0.87

Calculation of Operating time of over current protection of Transformer Feeder Current Setting in % (PS) Current Setting (I>) (CTR X PS) Fault Current considered (Amps) (I) Operating time calculated as follows

0.9 225.00 25000

1 >

+ K
IEC Very inverse (A) (B) 13.5 0

1 >

Selected Characteristic Time/current curve group Very inverse C K (TMS)

1 1

Operating time of Over current protection,t (sec)


II Calculation of required TMS for Incomer Feeder Fault current considered (A) Current Setting in % (PS) Current Setting (I>) Operating time calculated as follows

0.1226
25000 100% 2500

1 >

+ K
IEC Very inverse (A) (B) 13.5 0

1 >

Selected Characteristic Time/current curve group Very inverse C K (TMS)

1 1

Operating time of Over current protection,t (sec)

1.5
0.529 0.92

Minimum TMS for discrimination Selected TMS considering that TIE between unit boards are closed

CHGEAR

RELAY COORDINATION BETWEEN INCOMER & OUTGOING FEEDERS OF LV SWICHGEAR

CTR 4000/1

I/C-1 CTR 4000/1

I/C-2

CTR 4000/1

B/C

A CTR 400/1 CTR 400/1

180/200 KW

180/200 KW

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