LV SYSYTEM 1

[shahzy101]

thread238-153053
i am facing same issue here . 160 amps mccb direct to ddt WITH DELTA SIDE with ELR ON IT. AND ITS GOT TRIPPING.
CAN YOU GUYS GIVE THE SOLUTIONS.

 

[wayne440]

Based on the details you provide, I respectfully submit that you follow the advice in the referenced thread- "You should consult someone with some practical experience and knowledge of your country's regulations to assists you."

 

[RRaghunath]

ELR has a 'non-operate' threshold in accordance with IEC 60947 and it is 50% of the set pick up. This means the ELR can operate for any current that is not less than 50% of set pick up threshold. That is low.
Moreover, the cables passing through the ZCT window give rise to residual current on ZCT secondary depending on centering of the cables (or lack of it rather).
Thus, it is advisable to use a regular earth fault relay that is available as an integral part of the protection module of the MCCB (LSIG instead of LSI).

 

[shahzy101]

Thanks for clear understanding. Yes we have mccb earth fault protection though. But dnt know y client proposed this before.
The cable which has zct going to aux ddt which has different sigle phase loads like air-conditioned lights and fans and ups.
And ELR has a max setting of 0.5 amps.
This will easily achieved as un balanced right.
If for such different loads we want to use ELR what u guys suggest of rated value.?

 

[shahzy101]

 

[RRaghunath]

Higher the pickup threshold setting, stable will be the ELR against against residual currents due to cable asymmetry / cable installation errors etc.
To my knowledge, ELRs are available up to 30A setting range. You may like to choose one such device. Also, choose the time delay, something like 1s to prevent maloperation during transients.

 

[NCTHAI]

Quick question - by any chance your cable gland ground connection pass through CBCT? This can cause tripping. See the image below. Ensure correct installation.