Kiribanda
Electrical
- May 6, 2003
- 698
Gentlemen,
It is a common practice to specify and install circuit breakers rated & tested per ANSI C37.06/ C37.09/ IEC 62271-100 on High Resistance Grounded (HRG) or DELTA-DELTA ungrounded networks, specially in industrial applications on 5-38 kV range. But the application of these HV/ MV circuit breakers on HRG or ungrounded networks had not been discussed in any of these standards and also there is no any special test requirement for this type of application.(It is true that special test requirement and labeling is needed in HRG/ ungrounded applications for LV MCCBs/ PCBs etc)
We all that know during a ground fault on a HRG/ ungrounded network, all the electrical equipments are subjected to over voltages (line to ground voltage now equals to full line to line)with respect to ground till the fault is cleared. As such, we specify VTs with higher overvoltage factors, cables with 133% insulation etc etc. What about MV circuit breakers?.
Therefore,
How can we justify the application of these normal circuit breakers on HRG/ ungrounded systems?
Kiri
It is a common practice to specify and install circuit breakers rated & tested per ANSI C37.06/ C37.09/ IEC 62271-100 on High Resistance Grounded (HRG) or DELTA-DELTA ungrounded networks, specially in industrial applications on 5-38 kV range. But the application of these HV/ MV circuit breakers on HRG or ungrounded networks had not been discussed in any of these standards and also there is no any special test requirement for this type of application.(It is true that special test requirement and labeling is needed in HRG/ ungrounded applications for LV MCCBs/ PCBs etc)
We all that know during a ground fault on a HRG/ ungrounded network, all the electrical equipments are subjected to over voltages (line to ground voltage now equals to full line to line)with respect to ground till the fault is cleared. As such, we specify VTs with higher overvoltage factors, cables with 133% insulation etc etc. What about MV circuit breakers?.
Therefore,
How can we justify the application of these normal circuit breakers on HRG/ ungrounded systems?
Kiri