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I have a CT with following data Ratio : 300:5 Class : C100 Burden : 0.1 ohm I don't have magnetisation curve for this CT. I want to calculate whether CT will saturate at fault current 3000A. Total Burden (Including CT secondary, CT leads and relay) is 0.45 ohm Excitation voltage (V) = (Fault...

Hi All, I have a feeder feed by Variable Frequency Drive (VFD)of 60-200HZ. I have breaker and CT after VFD. Is there any effect on CT and breaker when frequency changes from 60 to 200hZ.

Hi All, I have a feeder supplied from variable frequency drive (50 -200Hz). This feeder needs a overcurrent protection. But digital relays are not able to provide protection for varialbe frequencies (50-200)Hz. Is electro-mechanical relay suitable for variable frequencies ? Or what other...

Is there any CSA requirement for the use of three independent pole breaker for capacitor and inductor switching to avoid trasients. I saw the use of independt pole breaker in 115 kv system for switching capacitor but not in 44kV system. Is there any CSA requirement ?

I got a call for first evaluation from one of the north american utilities for technologist position in substation job. the evaluation process says a series of standardized tests to measure problem solving, mathematical and special reasoning skill. The test runs for 3 hours. Do anybody have...

Hi everyone, The CT has following tapping 1. X1-X4 3200-5 2. X1-X3 2400-5 3. X1-X2 1600-5 and if accuracy of CT is says 2.5L200@2400A what it means ? we get 2.5L200 accuracy when we use tap X1-X3 or we get 2.5L200 accuracy whenever primary current is 2400A irrespective of any tapping...

Hi all, What is the maximum over voltage that could arise in four wire system with multiple ground points when system fauls occur (L-G or L-L of double line to fault or any other type) Thank you in advance for your reply.

Hi all, In North America I saw four wire Transmission/distribution system for upto 27.6kV system. What is main purpose of neutral in such high voltage as all loads are three phase only in this voltage range. Thanks in advance for reply.

Hi all, I saw the short circuit rating of a distribution system as following 1. for 27.6/16.0 kV 16kA 2. for 13.8/8.0 kV 34kA 3. for 2.4/4.16kV 56kA Why short circuit rating is higher when system voltage is small compare to higher system voltage ? Is not higher short circuit...

Hi everbody, what is basic rule for selecting lighting arrester for 13.8KV four wire system. Is there simple formula? Thanks in advance for reply.

Hi all, Hi everyone, I have voltage regulating transformer, 27.6kV/27.6Kv, Delta/ star. This transformer need to connect in 4 wire system both sides (Supply and load) I can connect 4 wire to star side of transformer. But in delta side of transformer where I should connect neutral wire...

Hi all, What is a special function of circuit switcher ? It is different than circuit interrupter ?

Hi all, I am looking some information on reneable eneggy. 1. How synchronous of inverter based generation is synchronized with grid ? it is same as synchronous generator with the help of synchronoscope or something else ? 2. What is common practise to connect solar power to grid ? I. PV...

Hi Everyone, I have interest in renewable energy and would like to know how below renewable enery connects to grid 1. Solar PV cells 2. Bio mass, biogas, biofuel 3. Wind 4. tidal I believe solar PV cell produce DC power, then it converts to Ac by inverters and so on. And more related to the...

Hi everyone, Can anyone explain me how BREAKER FAILUR INITIATE works ? I have a scheme having Bus bar with 3 outgoing feeder and 1 incoming feeder. If outgoing 1 fails to trip, then Breaker failure relay at outgoing feeder 1 sends trip signal to trip outgoing feeder 2, outgoing feeder 3 and...

I saw automatic transfer switch with 4 pole where neutral of both source connected to one pole of switch and neutral of both switch never mixed. I saw automatic transfer switch with 3 pole where 3 phases are connected to 3 poles and neutral is connected to common neutral bus. In this case...

I saw a 132kV capacitor beaker with three individual pole operating mecanism. obiviously the breaker has three separate individual trip coil for three poles. Now for supervison of trip coils, In my opinion, we need three separete coil relay (could be a one reay with three coils) I saw single...

Is there any zero sequence current in delta connection ? For Star/Delta transformer, if there is single line to ground fault in delta side of the ransformer, how zero sequence current flows ? Thanks in advance for your answers. Pukar

Dear all, What is ANSI tripping band voltage for 250VDC system. I know that ANSI tripping band voltage for 125VDC system is 70V to 140V. but do not know tripping band for 250VDC system. I am working in 145kV ABB breakers which has tripping system of 250VDC. is there any way, any link, where...

Dear All, I saw 145kV transmission system where switching of shunt capacitor is done by three induvidual pole circuit breaker replacing three pole ganged circuit breaker. What is the main reason behind this ? in my opinion, main purpose is that when one phase of capacitor gets fault at that...