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@wauld VLF = Very Low Frequency PD = Partial discharge TD = Dissipation factor measurement (tan delta) The TD and PD diagnostic methods complement each other ideally Dissipation factor measurement (tan delta) A reliable diagnostic method for determining the general condition of a cable...

There is 110 Vdc tripping system + batteries :). My question is related with the faults that can happen inside the motor and the breaker will not be tripped because of the fault with the tripping circuit itself. There is nobody in HV room, so such an alarm from a TCS relay can go unnoticed...

Well in this case that's bad news. The problem is that our plant is an island from power point of view. We have turbines and there is a possibility that the under voltage condition to occure. And we have 5 motors in the same condition that I described. There is a small possibility that the...

Guys, Thank you very much for your answers. @applekor: the undervoltage contact was in the old scheme (fuse-contactor) and will be present as well in the breaker new design. I found this with google: 'A TCS relay is used to monitor the integrity of a circuit breaker's trip coil and associated...

In our plant has been decided (because of bad design) to replace fuse-vacuum contactor protection scheme for a motor with breaker protection. The motor is 5MW, 11kV. For this purpose an entire switchboard will be changed. The existing motor protection relays will be re-used. One of the relays...

Check auxiliary contacts of relays/contactors (which are doing the star/delta sequence) and the control diagram of the star/delta panel (can be bad contacts in the control wiring). Sometimes there is a problem with the above mentioned items (at least I had the same problem like you and it was...

14, What you want is not practical. I would say if you want a practical approach : you can try to reduce the power consumption by adding a power economizer (eventualy by doing this you can reduce the power consumption with 20-30%) I've been working in plants with a lot (I mean a lot!!!) of...

itsmoked, I think you are right! There is an issue in the electrical design literature if you are using earth leakage devices (or if you want so called RCCB) that the computers are having 3.5 mA earth leakage to earth all the time(because of filters). This is the reason that it is not...

The slightly overload of a HV motor it's common practice in a gas plant. The O/L protection behavior should be described in the Protection relay setting study of the electrical system of the gas plant where you are. Have a look in this book and check about overloading of the motor info. For...

rmw, North Africa, but we contact the company from UK as they do not have a local agency for customer service.

Well rmw, I've got one input: their customer service sucks ! Especially if you need them on emergency basis.

Our plant is located in the desert, where temperatures bellow zero are not common. The temperature is between 5 and 45 °C and I've seen toasted capacitors for the same case that you are debating here.

Sometimes can happen like this, with large low voltage motors. Try to have the wiring in the middle of the earth leakage CT. During the start because of the flux is not uniform can give false earth fault trips. If is posible, try to adjust the current as well (try 1A OR 2A set point). 600 mA...

There are two issues here: 1. You can try to approach the energy waste by switching the transformers on/off manually or you can buy an energy management system which would do this for you. We need to probable to revise the maintenance procedure (to decrease the time between the maintenace...

Hi aolalde, Sorry you are right :) , I did not mention the speed: 2980 r.p.m. So according to what you all gentlemen say, the situation at the moment is like this: in case of the motor stall at start-up the motor will trip after 13 s (the setting from IMM-7960), because the speed sensing relay...

@ jraef: The starting method is DOL (there is no any possibility to adjust the speed). The motor are not undersized. (are running loaded 80-90%, some times for short period of time 105-110%) The speed sensing relay can be adjusted. @ GordS and aolalde: The speed sensing relay was not installed...

Hello to all! I’m very glad that I discovered this excellent forum. I have the following issue for you. I’m a maintenance electrical engineer in a plant with several HV motors 11kV/ 5.3 Mw electrical motors. The motors are protected by IMM 7960, multifunction relay (CEE relays made - UK). At...