Dear 7anoter4,
Thank you for your reply.
I have contacted the MV Switchgear manufacturer.
He explained that the design of the cable earthing switch has not changed but they had decided to test the earthing switch for single phase to earth fault.
The result is that the cable earthing switch...
Hello,
I would like your thoughts on the following situation.
We are about to order an Air-Insulated, Metal-Enclosed, Medium-Voltage Switchgear according to IEC 62271-200.
The switching-device compartments are equipped with withdrawable Vacuum circuit-breaker.
The feeder earthing switch can...
Hi,
I need to write a "quality plan" to configure numerical protection relays in order to ensure a numerical relay is correctly configured.
This quailty plan would be like a check list with the different steps to follow.
The steps could be :
1. Identify relay hardware configuration , the...
Hello,
I would like to know if anybody has experience in electrical protection for double fed asynchronous machine for pump storage application and also for double fed asynchronous machine in general.
Which electrical protection are needed?
Which protection relays can be used (ABB, GE, SEL...
Davidbeach thanks for your answer!
I was not sure if the generator protection relay has also to provide protection of the synchronous generator during the time it is used as a motor.
The reason for this is that GE has a technical note explaining that their generator protection relay can track...
Hello,
We want to select a generator protection relay for a gas turbine starting with a Static Frequency Converter.
This relay must protect the generator during startup and normal operation.
The generator is used as a motor to start the turbine.
Once the turbine is started the generator...
Thank you all for your replies.
We will split the signals.
When paralleling two independent 125Vdc power supply diode, everything is ok until there is a ground fault.
Usually the voltage is -62.5 Vdc and +62.5 Vdc.
The two (-)of the power supply are connected together and the 2 (+) are...
Hello,
The problem is following: we have 2 redundant numerical differential protection relays for a generator step up transformer.
Each numerical relay has it own separated 125 Vdc power supply and lockout relay.
There are 2 separate channels.
We receive only one dry contact (not 2) for each...
Thank you for your answers.
Find attached the steam turbine datasheet.
Its potential max power is 1000 kW.
The steam conditions are also given.
According to your mails, i would say that the steam pressure is higher than rated.
During normal operation, the steam throttle valve is slighty open...
Hello,
I would like your thoughts on the following situtation.
A steam turbine of 750kW (480V) had a governor failure and the steam valve was fully.
The load on the bus to which the turbine is connected was 1200 kW.
The intertie relay tripped on reverse power because active power was exported...
What are the electrical protections necessary for a 900 KVA induction generator connected to a steam turbine?
Is an asynchronous motor protection relay enough or is a synchronous generator protection relay necessary?
The loss of excitation protection 40Z is for sure not necessary.
In case of...
My sources for equivalent current calculation are GE and Basler.
If you have more ideas about the K factor, i 'am interested.
http://files.engineering.com/getfile.aspx?folder=447afce3-d3cb-431b-9602-ae887ead6eae&file=Basler.bmp
Thanks for your answers.
Sorry for the mistakes that you have perfectly corrected.
When you say:
"Take P = Ieq^2*R1 and what do you get?
P = R1*I1^2 + R2*I2^2"
I assume R1, R2 are the rotor positive/negative sequence resistance.
P seems to depend only on the rotor resistances. What about...
In motor protection relays, the thermal curve element (49TC) models the thermal capacity in a motor.
The 49 thermal element takes the load level and negative sequence current into account to creates a thermal model of the motor. Thus the thermal model creates an "equivalent current," Ieq, that...
Hi,
This is just to let you know that the generator has been synchronized.
As foreseen, the zero sequence voltage on the ungrounded Delta side of the transformer has disappeared once the unit has been synchronized (referenced to ground).
Thanks again for your help
Thanks for your answer David.
I conclude that the settings of the relay were to sensitive.
If a broken delta transformer with a resistor is used to measure the zero sequence voltage would it change something?
What is the mimimum 3V0 setting recommended for a zero sequence overvoltage relay...
Hi Waross,
Usually i also see that the generator is connected on the DELTA side of the transformer, but here it is not the case.
What difference does it make? what is the advantage? is it linked to 3rd harmonics?
The WYE points of the 5MVA transformers are floating.
The generator is connected...
Hello,
We have a unit connected generator.
The generator is 11kV, 9MVA and is medium impedance grounded (25 ohms).(high impdedance would have probably been better)
The generator is connected to 2 step up transformers of 5 MVA connected in paralell.
Both transformers are exactly the same and the...
