Dear Folks,
I am looking for an AVR, which can able to regulate the voltages at both secondaries of three winding transformer. OLTC is located on primary winding of the transformer
If such AVR available, please suggest me.
Advanced thanks.
Dear Folks,
Pl. clarify the different ratings of surge arrestor given in brackets (for 13800V system) as per IEEE C62.22-1997, table No.7 attached herewith.
Advanced thanks...
Dear Folks,
Pl. clarify regarding breaking current selection of LV ACB, if L-G fault current is more than 3-ph bolted current , which current needs to be considered for LV ACB breaking capacity? I read somewhere that we need to consider 3-ph bolted fault current to select LV ACB breaking...
Dear Folks,
Two issues are confusing me in regard of VFDs.
1. What is the Power factor of PWM type VFD type with Line choke (source side)? As DC link capacitor is there, and motor always take reactive power from capacitor, I assume unity power will maintain at line side. Anyone pl. confirm.
2...
Dear Folks,
Pl. clear the doubt on softstarters. Does soft-starter for motor generate harmonics, if it operates at full output voltage (no voltage reducing condition)and without by-pass contactors?
Advanced thanks..
Dear Folks,
Please clarify the following:
How power Cable "ambient temperature de-rating factor" will depend on different protection systems?
In one of the cable catalogues it is given as follows:
for Example:
Ambient temp: 50 deg.C
Semi enclosed fuse to BS 3036 : 0.91 (Derating factor)
Fuse to...
Dear Folks,
I have seen that one Power transformer has 3 star connected windings and one Tertiary winding (Y/Y/Y/D). Tertiary winding is not loaded.
PTs for power transformer secondary windings have also 3-winding. one primary star winding, one secondary star winding and one open-delta (broken...
Dear Folks,
I have started power system modelling very recently. For generator modelling, in X"/R -ratio, which resistance we have to consider? between phases or phase to neutral (for star winding generator)
I tried with both resistances for calculaing Transient and sub-transient fault currents...
Dear Folks,
CT Knee voltage for differential protection shall have more than two times of Vk
Vk=If (secondary) x (Rct+ 2xRL)
What is the above fault current - 1/2 Asymmetrical rms / 3-cycle Asymmetrical rms / 3 cycle symmetrical rms.
Advanced thanks for your replies
Dear Folks,
what is the minimum rating of Distribution transformer (11/0.415kV) requires to provide oil sump? And which standard gives this information.
Advanced thanks for your information.
Dear Folks,
If three same rated generators are connected in parallel and only one generator neutral is connected to ground through NGR (neutral grounding resistor, ground fault current restricted to 300A). Let us say Generator no.1 neutral is connected to ground.
For generator No.2 terminal...
Dear Folks,
Pl. advice me for breaker and Switchgear ratings.
We have 9-AC generators are connected in parallel without grid supply. All neutrals are solidly grounded without neutral breaking during parallel operation. Fault levels are calculated by ETAP software and these values are as follows...
Dear Folks,
In one of the ships, all 3-ph AC generator neutrals (9NO.,) are solidly connected to Ship hull. Pl. suggest me, is it require to calculate Touch and step potential?
Generator rating:
110kVA, 415V AC 3ph, 60Hz
Advanced thanks
Rajesh.T
Dear Folks,
In our project specifications, I have seen the sizing calculations of transformer and is calculated by:
(continuous load X 1 + Intermittent Load X 0.3 + Stand-by Load X 0.1) X factor of safety(1.2)
Anyone pl. explain how to calculate factors for intermittent loads and stand-by loads...
Dear Folks,
I am new to this forum. Could you pl. explain me the difference between corrosive current and conventional current (impressed current to avoid corrosion)?
Advanced thanks...
Dear Folks,
Recently we have measured polarisation Index (PI) of one MV motor-11kV, 5100MW, we got the following values.
R -E --- 4
Y -E ---- 4
B -E ----4
R+Y+B-E --2.5
Anyone pl. discuss the reason for less PI if we measure all windings with respect to ground.
Thank you..
Dear Folks,
Pl. explain me the significance of oxygen in transformer oil for both Bagged type conservator/ open type of conservator.
Advanced Thanks...
Hi Friends,
We have a motor of 3.3kv, 450KW. This motor is going to get supply from 3.3kv switchgear, which some times operated by grid supply and some times by Generator supply.
Grid system is having solid ground neutral system.
Generator is Resistive ground.
My Question: What should i...
