Test Specification 10.02

Response of protection subsystem to various kinds of voltage disturbances

Test Specification Definition

ID

10.02

Reference to Test Case

TC10

Title of Test

Response of protection subsystem to various kinds of voltage disturbances

Test Rationale

This test is an extension of TS10.01 in the sense that the protection subsystem is tested in terms of voltage limits. Due to the fact that the voltage at the PCC is determined by the local configuration of the microgrid, a detailed microgrid topology is used instead of one lumped load.

Specific Test System (graphical)

The above test system is based on the LV distribution network benchmark application example by CIGRE1

Target measures
  • ΔVmax=+15% to -20% of nominal voltage
  • Response time (Relay and Switch) <0.5s
Input and output parameters

Input parameters

  • Voltage at PCC
  • Power flow at PCC
  • Relay state

Output parameters

  • Breaker state
  • Voltage at PCC
Test Design

The test is conducted into two distinct steps each of which tackles one voltage threshold (i.e., +15% (265V) and -20% (184V). It is presumed that in between these steps the relay is reset to its normal state in order to allow for the detection of the next disturbance.

Initial system state
  • The source and the microgrid are operated in a way that leads to a voltage at the PCC within the protection limits i.e., 184V< Vpcc < 265V.
  • The breaker (static switch) is closed, therefore the microgrid exchanges power with the grid (voltage source).
  • The protection relay is reset to its normal state
Evolution of system state and test signals
  • At first the voltage at the PCC should be within the protection limits and the microgrid should be connected to the grid (LV source) and exchange power.
  • Either the LV source or some of the microgrid units should be controlled in a way that allows the voltage at the PCC to increase towards the upper limit (15%). The time that the voltage crosses the limit is recorded.
  • The protection relay detects the disturbance and activates a disconnection of the static switch.
  • The static switch disconnects the microgrid from the LV source. The PCC voltage is monitored in order to detect the disconnection time and calculate the response time of the protection system.
  • The relay is reset and the static switch reconnects the microgrid to the source.
  • Either the LV source or some of the microgrid units should be controlled in a way that allows the voltage at the PCC to decrease towards the lower limit (-20%). The time that the voltage crosses the 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 PCC voltage is monitored in order to detect the disconnection time and calculate the response time of the system.
Other parameters

N/A

Temporal resolution

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

Source of uncertainty

Uncertainties may arise due to the precision of the various instruments used to measure the voltage responses. Additional uncertainties may be introduced by the communication channel delays between the protection relay and the static switch, as well as from the operation of the microgrid units that are subject to:

  • Environmental conditions
  • Consumers’ demand
  • Grid parameters variability i.e., resistance/inductance ratio
Suspension criteria / Stopping criteria

The test should be suspended and restarted if one of the quality attributes described in the TC is not met.