We have an analog input module (Adam 4017) that needs to be connected to our data constrictor; they communicate via RS-485. The analog module has two pins (RS485+, RS485-) dedicated for communication.
Instead of buying RS-485 cable/converter to connect these two modules, I was wondering if I can...
Could somebody give a primer on Stuck breaker protection, beyond the basic understanding (i.e. these are used in case a breaker is not tripped when asked to do so; a timer starts when the trip signal is sent and when the timer expires stuck breaker initiates and trips other breakers around that...
Hello
To expand my knowledge on Electrical Engr subjects, I am assuming a new role as Protection and Control Engineer. I am told I’d be dealing with a lot of relay setting calculations and communication network issues involving, RTUs.
What book/material would you recommend for me to not only...
Hello
I’d like to practice the power flow analysis, short circuit modeling etc I had learned few years ago on my personal time. My company doesn’t have any of the tools such as SKM Power Tools or ETAP. As such, I want to personally invest on this and practice myself.
Any suggestion as to where...
Hello
We are considering replacing the current revenue meters (CT/VT) for our 230 kV line (secondary of the GSU). The accuracy and burden and most other specs match.
However, we need current ratio of 1000:5 and the unit that the vendor is offering has multi-tapped ratios: 200/300/400 X...
We have to cut a small section (about 3 feet) of our non-seggregated 10 kV bus bar (all three phases) since the ends are not aligning with the bar holes at the generator end (other end of the bus bar is connected to the transformer low voltage bushing stubs). Instead of cutting the bar at the...
Our Transformer standard specifies that Bushing ampere rating shall be at least 20% higher than the respective transformer winding ampere rating at maximum transformer nameplate rating.
Does anybody have a basis for this standard? I checked c57.19 series on bushings but couldn’t find anything on...
I know that the zero percent impedance of a transformer is important primarily for fault calculation and could effect reactive output. However, if a transformer spec doesn't specify this value, how do we obtain this? We have an old transformer (750 MVA, 24 KV to 230 KV GSU-Westinghouse) with...
Can somebody please explain why the asymmetrical current calculated using Total current method is significantly
different to that calculated using Symmetrical current method? I know the X/R multiplier is different for these
methods, but why should a fault current (asymmetrical) calculated using...
Folks,
Got a question on rating a HV circuit breaker.
Say the fault the breaker sees, as calculated by ASPEN, is:
ISC=54597.4 Amps
3LG_AMPS=60602 Amps
For a given X/R=38.4.
Question: What is the minimum interrupter rating (both symmetrical and asymmetrical) for a breaker to interrupt this...
Have a question on short circuit study on our system.
Shown in a 115 kV system model. The model is missing a generator synch breaker at Point A and we are interested in the maximum available fault as seen by this breaker. The model calculates the fault on 115 kV Bus (say point B). Is this fault...
We are planning to replace an old 138 kV OCB (Westinghouse) for a new one with higher rating. The available fault on the system is 73kA asymmetrical which corresponds to 51kA symmetrical (X/R =39.1). We are struggling with what interrupting capability does the present breaker have. The nameplate...
Recently we had a lightning event in our plant and although we didn't see any visual signs of damage, we had the unit trip due to operation of a lockout relay. This relay is an elecromechanical relay, not susceptible to seismic events or vibrations. This relay gets input from various other...
We are procuring a 607MVA transformer (345 KV to 22 KV) which we are storing as spare. As for the grounding requirements, while the transformer stays de-energized as spare, we were provided with three #4 gauge wires. We want to know if there is a spec (IEEE or ANSI) on such requirements...
We have a GSU transformer that has been running for over a year now. There are two support bars holding a conservator tank over the main tank. These bars are between phase A and C (two bars are right above phase B) low voltage bushing box.
We recently noticed overheating in the bolts in these...
Just a survey question. Would appreciate if you can reply.
The local winding temperature gauges (analog, Qualitrol) on our GSUs are connected to the CT on HV windings. When we loose power to the cooling cabinet of the Transformer (that powers fans and pumps) we still get the winding temperature...
Hello all
If my transformer has the following rating:
337200 KVA with ONAN cooling (55 deg C rise)
What does that mean?
I am guessing with only natural oil circulation/cooling (no fan/pumps), the transformer is rated for 337MVA output, right? Then what is 55 deg C rise? Does that mean after the...
Folks
We suspect some problem with our dry transformer 6.9 KV to 480 Volts step down.
We did phase to ground megger testing and didn't find any problem. What other test do you suggest to conform the transformer is working fine? We are going to recommend an impedance check of the primary delta...
Folks
We suspect some problem with our dry transformer 6.9 KV to 480 Volts step down.
We did phase to ground megger testing and didn't find any problem. What other test do you suggest to conform the transformer is working fine? We are going to recommend an impedance check of the primary delta...
We have a 27,900 gallons capacity transformer tank, with two small elliptical conservator tanks on top. The conservator tank has an air bladder inside and is filled with transformer oil (except for the air bladder).
We want to know the exact oil level on the transformer without going to the top...
