The ENA recommendations for G59 give the required settings for generators to connect to the Grid, witnessed on-site by the Distribution Network Operator (DNO).
The protection functions defined are for Calibration and Accuracy Tests with the implementation of Stability Tests for voltage, frequency, and Rate Of Change Of Frequency (ROCOF).
For the Small Power Station protection, the settings might be for 110V LV Protection or 230V HV Protection. Over and Under nominal values are 2 Stage functions.
Even though the nominal voltages are defined as either 110V or 230V, a sitespecific voltage could be implemented.
A particular change has been made to the ROCOF settings. It has now been redefined to be either 0.5Hz/s or 1Hz/s with a tripping time between 0.5s <t> 1s.
ROCOF is now defined with very specific stability settings. The duration of a stability test with a ROCOF of 0.5Hz/s must be 4.4s, from 49Hz to 51Hz. With the OMICRON test set, this can be very easily implemented.
Some DNOs witness the testing are not in favour of a fully automated test file and prefer to view tests one-by-one. OMICRON is well known for its automated test files, but we have a G59 Test Template that can be run without automation.
Tests can run one-by-one as the DNO requires with the added advantage that the report is created at the same time and in a 1 page format. Detailing limits, Pass/Fail criteria and results recorded as Ph-Ph (HV) or Ph-N (LV).
With the OMICRON Test Universe software, the Test Template contains all the test files required to successfully test a relay programmed with G59 settings. One big advantage is that the only function required to be disabled for testing is ROCOF. All Stage 1 protection settings can remain active. ROCOF tests are the last to perform so the user will not forget to re-activate the function.
The ENA settings are already loaded in the test file, the user only has a few parameters to set that will be particular to the site under test.
It is easy to set these settings within the software. Here you can set the correct HV or LV, System Nominal Voltage level, Pre-fault time to allow the relay to stabilise before testing, and the option to select whether the relay has a Start Contact or not.
The only other settings to set is for the ROCOF.
The DNO can review each test result as it is made, and if desired, can re-run the test with the new result overwriting the previous in the Excel Report.
With stability tests, for example the UV Stage 1, we generate a graphic of the result where we see the change in applied voltage, and that monitoring of the trip contact showed it remained inactive.
The DEA Interconnection G59 Test Template can be downloaded for free from the Protection Testing Library (PTL) in the Customer Portal on our website. www.omicronenergy.com