Test Specification 10.01

10.01

TC10

Response of protection subsystem to various kinds of frequency disturbances

This test is necessary in order to verify the protection relay’s capability of detecting the specified disturbances as well as to verify that the response time of the static switch in disconnecting the microgrid is below a specified threshold.

The above setup allows the evaluation of the frequency protection function with only one load in place of a detailed microgrid since frequency deviations are due to larger-scale disturbances in the transmission system.

• Δfmax<±0.5Hz
• ROCOFmax <1Hz/s
• Response time (Relay and Switch) <0.5s

Input parameters

• Frequency
• Load consumption
• Relay state

Output parameters

• Breaker state
• Load voltage

The test is conducted into three distinct steps each of which tackles one frequency threshold (i.e., 50.5Hz, 49.5Hz, and ±1Hz/s). It is presumed that in between these steps the relay is reset to its initial state in order to allow for the detection of the next disturbance.

• The source frequency is within the operating limits i.e., 49.5Hz < f < 50.5Hz, and –1Hz/s < ROCOF <+1Hz/s).
• The breaker (static switch) is closed, and therefore the load is supplied.
• The protection relay is reset to its normal (initial) state

• The LV source frequency is monitored and, controlled in order to increase stepwise to the maximum allowable value of 50.5Hz. The time of this activation limit is recorded.
• The protection relay detects the disturbance and activates a disconnection of the static switch.
• The static switch disconnects the load from the LV source. The load voltage is monitored in order to detect the disconnection time and calculate the response time of the system.
• The relay is reset and the static switch reconnects the load to the source.
• The LV source is controlled to change its frequency stepwise to 49.5Hz. The time of this activation limit is recorded.
• The protection relay detects the disturbance and activates a disconnection of the static switch.
• The static switch disconnects the load from the LV source. The load voltage is monitored in order to detect the disconnection time and calculate the response time of the system.
• The relay is again reset and the static switch reconnects the load to the source.
• The LV source is controlled to change its frequency gradually upwards or downwards with a ROCOF equal to 1Hz/s. The time of this activation limit is recorded.
• The protection relay detects the disturbance and activates a disconnection of the static switch.
• The static switch disconnects the load from the LV source. The load voltage is monitored in order to detect the disconnection time and calculate the response time of the system.

N/A

A sampling time of <1ms is required for the accurate measurement of the protection time response

Uncertainties that may appear in this test are due to the precision of the various instruments used to measure the voltage/frequency responses. Additional uncertainties may be introduced by the communication channel delays between the protection relay and the static switch.

The test should be suspended and restarted if one of the quality attributes described in the TC is not met. Also, if the frequency variations are well above the specified limits (i.e., 0.1Hz and 0.1Hz/s) the test should be discarded and repeated with the appropriate values.