I would like to discuss an issue being facing in our Power plant(90MW). Our plant generation voltage is 11KV & Plant auxiliary & MCC voltage is 400V AC 50Hz. We have two sections of Power plant PP1 & PP2. In PP2 we are facing issue in LV MCC Panels.
In LV system we have two BUS A & B. Both BUS's are getting power from their individual T/F(11KV/400V AC) & from here power is distributed to various MCC panels in plant.
Booster no. 1 MCC have two LV breakers(Q1 & Q2) which are getting power from BUS A & B.
During last week we were found that Q1 breaker incoming cable insulation was melted around the cable gland area & checked the other glands also & they are also found overheated with abnormal temperature. then we took changeover to Q2 breaker but this is also now getting overheat. In main LV distribution panel side also cable glands are getting overheat which are connected to Q1 & Q2 breakers in MCC.
In one phase two cable are laid & connected, size is 400 sq.mm Armoured cable. R phase(L1 & L2), Y Phase(L1 &L2) & B Phase(L1 & L2). The current also not equal in two length of each phase.Pl see the below readings.
| Line |
| Without Armoured |
| With Armoured |
| R Phase |
| L11 |
| 195 A |
| 328A |
| 115A |
| 174A |
| L12 |
| 137 A |
| 72A |
| Y Phase |
| L21 |
| 103A |
| 332A |
| 145A |
| 306A |
| L22 |
| 167A |
| 175A |
| B Phase |
| L31 |
| 150A |
| 328A |
| 120A |
| 317A |
| L32 |
| 183A |
| 199A |
without armoured = Cable outside of MCC before entry in panel.
with armoured = After gland inside the panel.
Team kindly go through the above said issue & your kind comments will be highly appreciated.
