Hi, I would like to get some information related to the storage of dry type transformers. What temperature settings should be used to trip the installed space heaters. Should the temperature setting be a litte above the ambient temperature? Is there any standard for this. Please assume that the...
For a steam driven turbo-generator, which protection is better for normal shut down procedure: Reverse power or low forward. The generator manual does specifically say to shut down the unit on low forward. Are there any disadvantages to using low forward tripping during normal shut down?
Hello. We have Siemens 400 V switchgear installed at our site. One of the load breaker supplies power to Active Harmonic filters. The CT on the breaker become heated up and faulty after some time. This has happened twice now. Please suggest what could be the reason for this?
We have a hydrogen generation (Stuart Cells) facility at our power plant. There is a hydrogen storage tank adjacent to the generation unit. These both areas under not directly under the radius of the adjacent lightning terminals. Should a new lightning protection be installed specifically for...
I wanted to know if the winding coils in a generator rotor expand radially due to thermal effect? Axial expansion is known but wanted to know about radial expansion due to temperature at high currents.
Thank you all for the responses. I have read somewhere that you can even plan the cleaning of panels with irradiation data. As soon as irradiation values fall below 200, you clean the panels.
We are supervising a 1.25 MW solar plant with 38 string inverters and around 5000 solar plates installed. It has been our practice to wash the solar plates on a daily basis. However, we are observing faults due to moisture ingress and the frequency of faults are increasing. Please suggest some...
Hello. I have a few dry type transformers installed at the power plant where I work rated up to 2500 kVA. The transformers have been in service since the late 90s. What are some techniques that can be utilized for remaining life assessment of these transformers? Any advice would be appreciated...
Hello. I have to translate stator earth fault settings from REG 316 to the newer model REG 316*4. I do not have the optical cable for communicating with PC. There is also a serial port at the back of the new relay. However, the relay is not communicating using the serial port (I used a 9pin...
There are 4 unmarked wires coming from the shunt motor. 2 for field winding and 2 for armature winding. What will be the effect of polarity of both windings if we connect it to the starter?
Thank you sir for the elaborate response. Just wanted your opinion on the external resistance for the field winding. Do we need that for the shunt motor?
The combined resistance of the armature and series winding of the original motor was around 0.6 ohms of armature resistance and 2.495 ohms external series resistance. Total 3.095 ohms. External resistance rated at 28 Amps.
DC supply is 240 Volts
I will get back to you with the resistance values...
Thank you for the replies. The current scheme with the compound motor has 2.495 ohms external resistance in series of armature winding which is bypassed in 0.8 seconds. Would the same starter scheme work for the shunt motor? The armature resistance of the shunt motor is 0.6 ohms.
Hi. I am facing an issue where a dc compound motor of 220 volts, 5.5kW has failed. I have an option of replacing it with a dc shunt motor of same rating. However, the compound motor had timed external resistance in series of armature winding in the starting circuit. Can we start the dc shunt...
If the utility meter only registers real power consumed, will the residential consumer have higher utility bill if there are low power factor appliances in the home (assuming no PF penalty)?
RRaghunath you are right. Actutally REF should have operated but in actual the S1 of Neutral CT is grounded in the field (wrongly so we are assuming), which led the current path as I have shown. Hope it is clear now. If we remove the ground on S1, the same fault would have caused REF operation...
Sorry guys I was stuck without an internet connection. We finally found the problem and it was a high resistance path in one of the GSU 220kV CT secondary phases. One of the "pole flash-over relay" coils was in the secondary circuit and it was open.
I have attached the three line drawing and...
We have a 430 MVA GSU (24/220kv Ynd)that tripped as soon as it was taken on load at around 30 MW. The only relay that picked up was "51G1N" HV side Neutral ground overcurrent relay. No other protections operated. The following activities were done:
1. Performed complete testing of the...
