The meter test is probably the most important test that you can perform on a relay because it can tell you a lot of information about the relay. However, interpreting the meter results can be confusing because different devices in the relay testing world use different references; assuming you understand phasor diagrams to begin with.
For example, if you were testing an SEL relay with RTS software and a Doble test set, each device would display the following angles during a typical meter test:
- A Phase voltage = 0 degrees, B Phase voltage = -120 degrees, C Phase voltage = 120 degrees
- A Phase voltage = 0 degrees, B Phase voltage = 120 degrees, C Phase voltage = 240 degrees
- A Phase voltage = 0 degrees, B Phase voltage = 240 degrees, C Phase voltage = 120 degrees
Which one is correct?
Can you figure out which angle measurements apply to which technology? If you wanted to test this relay properly, you should be able to figure out the “right” angles for each one.
The following video is a preview of our Online Course 1-2: Phasor Drawings for Relay Testers which will give you an introduction to phasor diagrams and help you figure out the correct angles when testing relays.
Can you figure out which angle system applied to which device now?
- A Phase voltage = 0 degrees, B Phase voltage = -120 degrees, C Phase voltage = 120 degrees: = ?Which device
- A Phase voltage = 0 degrees, B Phase voltage = 120 degrees, C Phase voltage = 240 degrees: = ?Which device
- A Phase voltage = 0 degrees, B Phase voltage = 240 degrees, C Phase voltage = 120 degrees: = ?Which device
Check your Answers here
- A Phase voltage = 0 degrees, B Phase voltage = -120 degrees, C Phase voltage = 120 degrees: = SEL Relay
- A Phase voltage = 0 degrees, B Phase voltage = 120 degrees, C Phase voltage = 240 degrees: = RTS Software
- A Phase voltage = 0 degrees, B Phase voltage = 240 degrees, C Phase voltage = 120 degrees: = Doble Test Set
If you didn’t get the right answers or made a lucky guess, we strongly recommend you stop now and enroll in the four hour Phasor Drawings for Relay Testers Online Course to help you follow along as we move forward with this seminar. Things start getting phasor-centric from this point forward and understanding phasors is an important part of relay testing.
You can download this cheat sheet to keep track of the different devices and their phase angle references when you are out in the field.
if I DIDNT KNOW BETTER AND HAD NOT TESTED ALL TYPES OF RELAYS AND ALWAYS USED THE POSITIVE ANGLE SYSTEM IN MY HEAD ROTATING COUNTER CLOCKWISE AND GOT THRU IT EVERY TIME I WOULD THINK AFTER THIS DEMONSTRATION I WOULD NEVER HAVE BEEN ABLE TO KEEP IT ALL STRAIGHT. IVE ALWAYS USED DOBLE TEST SETS AND ALWAYS USED THE POSITIVE ANGLE SYSTEM DOING GE SWITZER BECKWITH BASLER GE SR GE UR SPIROTECS AND IT WAS NEVER AN ISSUE GETTING THE RESULTS I EXPECTED. NOW I QUESTION EVERYTHING. I THOUGHT THE ELECTRIC ENGINEERING WORLD ALWAYS WENT 0 TO 360 IN A COUNTERCLOCKWISE DIRECTION NOW YOUR TELLING ME NOT SO. I WANT TO SCREAM
I thought there was only one angle system also… until I went to the job I tell in the video for Course 1-2: Phasor Diagrams for Relay Testers (4 NETA CTDs) .
This doesn’t have a button to make as complete!
Thanks for reaching out. I see it on my end, so that must mean that you’ve already marked it complete.
Do all of these relays use the same method to report power factor?
I’m not sure. The only time I ever had to pay attention to power factor was when I was creating an automation system for a induction furnace using metering control software.
The most I’ve thought about can be found here (https://relaytraining.com/understanding-the-great-leading-vs-lagging-power-debate/) but I am only indirectly writing about power factor as lead or lag.