EC456 Power System Protection Lab #1 Overcurrent Protection Relay Learning Objectives: Understand the building blocks of a numerical protection relay Understand the HMI of the relay. Establish communication between the numerical relay and computer o Setting the relay o Monitoring the relay status Set the relay parameters for the given system Inject balanced rated load to the relay and monitor its measurement online Test IDMT characteristics of the relay and plot the theoretical and actual IDMT characteristics Equipments used 1. SEL351 Overcurrent relay 2. SEL AMS relay low voltage test kit Pre-lab assignment For the section of the power distribution system shown in Figure 1 below, find the current pick-up, time dial for relay Ra. The setting of relay Rb is given below. Use the IEC normal inverse curve given by Equation 1.1 for co-ordination. 0.14 t = TD Equation 1.1 0.02 I f 1 I p I f Where: M= Multiple of pick-up setting I p TD Time dial setting Setting of relay Rb: Pick up setting = 5A; Time dial = 0.3 Figure 1. Pre-lab assignment.
Procedure Understanding the relay setting 1. Open AcSELerator software, for communicating with the SEL351 relay (icon on the desktop). 2. Open the setting file Lab #1 (In Settings => Open, select Lab#1) 3. Go through the Group 1\Set 1\ General Settings menu and check the relay general settings: Figure2. General settings The relay has been set previously to the following data: CTR Phase (I A, I, B IC ) CT Ratio, CTR:1 2000 - equivalent to the ratio of (10,000A : 5A) PTR Phase (V A, V B, B VC) PT ratio, PRT : 1 100.00 (11,000/110) - equivalent to the ratio of (11,000V : 110V) Change the phase and neutral CT ratio for the relay Rb defined in the Pre-lab. 4. Go through the Group 1\ Set 1\ Phase Time Overcurrent and check if Time Delayed Phase Overcurrent element is enabled (51T). The selection on the top dialog box must be set to 1 ECE 456b Lab #1 / 2008 2
Figure3. Phase Time Overcurrent settings The pick-up setting is set to: 5.00 A The IDMT curve is selected as C1 (IEC normal inverse) 0.14 t = TD sec 0.02 I f 1 I s The time dial setting is set to 1.0 Change the pick-up setting and time dial setting for the relay Rb defined in the Pre-lab. 5. Check the programming of the output contacts in the Group1\Logic 1\Output Contacts section of the setting file. The OUT 101 Output Contact supposed to be set to TRIP. Figure 4. Output contact settings ECE 456b Lab #1 / 2008 3
6. Save setting file and send it to the relay SEL-351. First from File menu select Save and store it in Lab#1_Rb. There are two File menus in Figure 4 - choose the one below. Then select Send from the same File menu and transfer settings file to the device. This procedure takes few minutes. Injecting a balanced load to the relay 1. We will use SEL-AMS relay low voltage test kit to test the relay 2. Start SEL-5401 software (icon on the desktop). 3. Open the front panel control interface of SEL-AMS from Run=>Front Panel Mode Figure 5. Front Panel settings 4. On the Front Panel set the three phase current values (IA, IB, IC) to 1.00A and set the phase angles of A, B and C phases to 0, -120 and 120 degrees respectively. Set the three phase voltages VA, VB and VC to 63.5 and phase angles of A, B and C phases to 0, -120 and 120 degrees respectively. 5. Press the start button on the software window. 6. Reset the SEL-351 relay by pressing the TARGET RESET button on the front panel of the relay. 7. On the front panel of the SEL-351 relay press METER button and read the data from the LCD display. 8. With the software running, switch to the AccSelerator window and select Meter & Control from HMI menu to monitor the relay status on-line. ECE 456b Lab #1 / 2008 4
Figure 6. Meter and Control window. 9. Read the data from HMI window. 10. Observe the three phase currents and voltages measured by the relay and compare with the values injected (Remember that the relay will display the values in primary). 11. Switch to the SEL-5401 software and stop the signal injection from the Front Panel module. Close the Front Panel module alone. Testing the IDMT characteristics 1. You have the loaded IDMT test file, which was created to test the operating time of the relay and plot the IDMT characteristics. Through this test, the relay is being tested for 5 faults. (M=2, 4, 6, 8 and 10) 2. From the SEL5401 software open the pre-created IDMT test file (File => Open, select IDMT.RTA file from the C:\ECE 456\Lab#1 directory). 3. Go through the 12-stage test sequence of the loaded IDMT file and understand what is being done. ECE 456b Lab #1 / 2008 5
Figure 7. Testing sequence settings 4. Download the test file and run the test by going to Run \ Download Test and Run it on the top menu bar. 5. Observe what happens. Wait for the testing to complete. 6. Note down the operating time of the relay from the result displayed after the test is completed. The measurements for each of the test stages are displayed on a Result window (Figure 8). Figure 8. Test results ECE 456b Lab #1 / 2008 6
7. Verify the obtained result with the expected theoretical value. 8. Plot the expected and obtained curves on the graph sheet. 9. Repeat the entire experiment for the relay Ra defined in the Pre-lab. ECE 456b Lab #1 / 2008 7