In my last publication I promised to tell about how could be useful mass start disturbance recorders, in one real working case, when happened weird trips of electrical equipment.
Well, we have inside substation switchboard 10 kV, 2 bus bars 10 kV, 2 incomers and bus coupler.
On the bus bars connected transformer feeders and high voltage motors. Transformers feed low voltage switchboards 0.38 and 0.66 kV.
On switchboard 10 kV we have FATS device (fast automatically transfer system).
Via FATS there was done manual changeover, change supply from incomer 10 kV to bus coupler without interruption of electrical supply.
And so, problems happened during this manual changeover 10 kV weirdly it was tripped low voltage motors 0.66 and 0.38 kV. Plus they was tripped not all, but always different; sometimes 1 motor, another time 3 motors.
At this point of time it was found no any logical regular dependency.
Disturbance recorders nowhere started in relay protection devices.
But what if to start disturbance recorders all consumers with Sepam 80, at the moment command manual changeover, as high voltage as low voltage?
As far as I knew precisely that happened during the manual command by button, it could be possible somehow to transduce that command to digital signal and to transmit that on start disturbance recorders all relay protection devices in substation.
Button on switchgear send command by the press of operator. Lucky for me on the button I found another second free contact, and I have in reserve development board Raspberry Pi b+
Free contact from button I connected to input GPIO Raspberry Pi (in python script I configured that as input)
For Rasspberry Pi it was written Python utility, which could to get command from button and GPIO and send in parallel mode command for start all disturbance recorders via Modbus TCP.
But there emerged another issue.
As far as relay protection devices on HV and LV switchgear was Sepam 80, particular attention should be given method of start disturbance recorders through Modbus TCP.
Officially external digital command could be given through additional modification flexible logic Logipam.
However on substation I had approximately 48 pieces of Sepam relay. In order to prepare logic for such number devices it was necessary heaps of time. Moreover most of them was in work. Also in Sepam 80 to download logic in device imply reload of device, and schematic there was done in such of way that during the reload circuit breaker obligatory shutdown.
Ostensibly situation almost going to 'say goodbye' with beautiful idea about mass start disturbance recorders.
None the less after some of the analyze I manage to found some of non-documented possibilities Sepam 80, when could be possible to start disturbance recorders through Modbus TCP without any logic modifications!
That possibilities I instantly implemented to my Python script for Raspberry Pi, successfully put to the test, and after all made start all disturbance recorders, simultaneously with operators command for manual changeover through FATS.
Oscillograms from all relay protection devices was downloaded for minutes (see - Python. Downloading of oscillograms from relay protection devices). In manual mode it could be taken couple days.
After analyzing records in same day I found reason why tripped low voltage motors.
There was given recommendation how to avoid such unwanted mode.
As well as with help of that written almost simultaneous oscillograms it was taken a lot of interesting information about processes happened in electrical grid at instance of manual changeover.