Rules and Guidelines
Want to participate in the discussions? Please read our Community Rules and Guidelines. Need some help? Visit Support and Answers.

  • State Not Answered
  • Locked Locked
  • Replies 28 replies
  • Subscribers 32 subscribers
  • Views 4371 views
  • Users 0 members are here
Options
You may also be interested in
This discussion is locked.
You cannot post a reply to this discussion. If you have a question start a new discussion

LV 400V AC armoured cable glands are geeting overheat(Temp. measured more than 60 deg C)

Rohit Sharma
Hello Electrical Team.

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.
Parents
  • 0
    OK so glands and gland plates are not ferrous but there are large currents in the armouring.  Most likely cause of heating is the relatively poor connections made by the glands to the gland plate and the large currents flowing through them.

    You need to get to the bottom of what is causing these.    They could be diverted neutral currents or due to potential differences across the earthing network between the cable ends.  (I am assuming you have both ends of the cable armour earthed through the gland plates?)  This will involve a careful examination of the connections (N &E) between the two transformers and panels and the earthing arrangements on the site.


    You haven't explained what the earthing arrangements are at the panels in question but you may well have to isolate the armour at the remote end to fix this after of course making sure that there is a proper earth for that switchgear and circuits.  I don't know what the normal practice is where you are but in the UK such single point bonding of large cables is normal and results in greater current ratings.  Separate arrangements are made for the earthing.


    Hope this helps


Reply
  • 0
    OK so glands and gland plates are not ferrous but there are large currents in the armouring.  Most likely cause of heating is the relatively poor connections made by the glands to the gland plate and the large currents flowing through them.

    You need to get to the bottom of what is causing these.    They could be diverted neutral currents or due to potential differences across the earthing network between the cable ends.  (I am assuming you have both ends of the cable armour earthed through the gland plates?)  This will involve a careful examination of the connections (N &E) between the two transformers and panels and the earthing arrangements on the site.


    You haven't explained what the earthing arrangements are at the panels in question but you may well have to isolate the armour at the remote end to fix this after of course making sure that there is a proper earth for that switchgear and circuits.  I don't know what the normal practice is where you are but in the UK such single point bonding of large cables is normal and results in greater current ratings.  Separate arrangements are made for the earthing.


    Hope this helps


Children
No Data

Join us to get the best from IET EngX.

Joining EngX lets you personalise your experience so you stay up to date on the topics that interest you, plus you’ll be able to make connections who are looking to collaborate, exchange ideas and more.

Join us Not now

Community Rules & Guidelines