Could you please help me, with brief instructions, on how to make my simulation work?
I have a feeder, with buses, loads, lines, etc, and one IED with 67N element at the first bus, aka the substation. There are also CT and VT. When I simulate a single line to ground fault, in some point of the feeder, and look the time-overcurrent plot, there is no way to have the 67N activated when it is set to forward (neither reverse) direction. If I set none to the direction (like 50N), it works.
Another situation: using 67 phase element, still simulating the single line to ground fault, it works forward, doesn't do anything reversed (so this is working as expected).
What am I missing to make the 67N operate? Is it something related to the zero sequence of currents/voltages? Do I have to adjust more configurations?
I appreciate any tips to understand what is going on.
Please send me the case sample and if I can not answer I will ask DIgSILENT support center as the licence user.
Srete
Hi Mr. Srete Nikolovski, thanks for the answering!
I've found this: besides the directional earth-fault element parameters, in the relay settings, there is also another group of settings regarding the polarizing (voltage, current polarizing). And that is placed in a different field that I was missing... I am almost sure that this was the problem.
But I am still simulating more, to be sure.
Thanks for your availability, I will try more here following what I said, if the problem continues, I'll ask for your help, thanks.
Everton
Of course that there are different fields in the dialog box that need to be checked and defined besides the forward and backward directions!
Srete
The 67N element is a directional overcurrent element that is used to protect a power system from ground faults. It measures the current in the forward and reverses directions and trips the breaker if the current in the forward direction exceeds the set value.
The 67N element does not operate for single-line-to-ground faults because the current in the forward direction is equal to the current in the reverse direction. This is because the fault current flows equally in all three phases.
To make the 67N element operate for single-line-to-ground faults, you need to configure it to measure the zero-sequence current. The zero-sequence current is the current that flows in all three phases in the same direction.
To configure the 67N element to measure the zero-sequence current, you need to set the "Zero Sequence Direction" to "Yes". You also need to make sure that the CTs are connected in a wye configuration.
Once you have configured the 67N element, it will operate for single-line-to-ground faults. Here are some additional tips for configuring the 67N element:
- The "Overcurrent Setting" is the value of the current that will cause the breaker to trip.
- The "Time Delay" is the amount of time that the breaker will wait before tripping after the current exceeds the overcurrent setting.
- The "Direction" can be set to "Forward" or "Reverse". "Forward" means that the element will only operate if the current is flowing in the forward direction. "Reverse" means that the element will only operate if the current is flowing in the reverse direction.
- The "Zero Sequence Direction" can be set to "Yes" or "No". "Yes" means that the element will measure the zero-sequence current. "No" means that the element will not measure the zero-sequence current.