Impedance Relays Training Modules

These four modules introduce you to different characteristics of distance relays.

The first is the Impedance Characteristic Module; this type relay measures Z. This measurement of Z has the same distance from the origin regardless of the direction. This is a non-directional relay (or perhaps "Omni-Directional"). This type of relay is frequently used as a carrier start relay or as part of an Out-Of-Step scheme.

The second training module is the Reactance Characteristic Module; this type of relay measures the reactance of the system. If the reactance measured falls below the set-point then this relay will operate. This relay also has trouble with directionality, as you will discover when you "operate your virtual test equipment".

The third training module in the set is a hybrid unit. This is the Rectangular Characteristic relay. There are some relays that, instead of adopting a circle or a lens (modified circle) as an operating characteristic, utilize a rectangle. Later versions of relays even adopt quadrilateral characteristics. In any case this training module introduces the relay tech to the possibility that relays can operate with many different characteristics or combinations of characteristics. Just like the first two modules, you have control of a relay test set. You control the amps, volts and phase angle. You see the impedance plot change on the R-X Diagram and you see your test set's indicator lamp light up when the relay contacts close.

The fourth module of this series is actually a

Mho Relay Train & Test Module. 

This module has a Lesson Page and Practice Adjustments Page like the other Impedance Training Modules. Additionally, this module has a test section.

The test section has all of the hair-pulling calibrations that an electro-mechanical Mho Distance Relay possesses.

You better practice your adjustments and study how the relay works; because when you go to the test section a random test is created.

This random test is like an evil test proctor looking over your shoulder. The relay is tweaked to different MTA and Reach settings. You are not told what these settings have been tweaked to.

You must determine these "As Found" settings.

You are then instructed to "Adjust" this virtual relay to a set of desired "As Left" settings.

Do not be complacent that this is easy. Every practice device that helped you learn about these relays has disappeared from the screen. The only things available to you are the "Unknown relay" and your relay test set. (After all, isn't that the way it is in real life?)

When you have completed your test you can turn to the Score Sheet Tab.

This sheet will tell you how you did.

It tells you the "As Found" settings that were randomly picked and the "As Found" settings that you claimed to have found.

It will tell you the "As Left" settings that you were supposed to have installed into the relay and it will tell you where you actually left the relay.

This is an ornery test module. It acts like an old electro-mechanical relay whose adjustments and components are still intact. The adjustments do not vary, but the frustrations are similar. 

Time Over-Current Relays

These training modules teach you a number of things; curves and testing.

The Training Module on Curves shows the technician how to plot a Time Over-Current Curve.

There is a built-in calculation for USA Very Inverse Curve in this module.

Select your Tap and Time Dial on the relay (just like you would in the substation) then apply your selected test current.

The relay is assumed to be perfect and you can "Plot" your pick-up points for the four over-current values of your test.

This allows you to see the relationship between current, time and the way that the industry plots the pick-up time.  

The Training Module on TOC Test shows, step-by-step, the needed actions to test this type of relay. This includes how to hook-up the test leads and how to read the curve.

Click on Step 1 - set the Pick-Up Point

Click on Step 2 - set the Time Dial

And on through the relay hook-up and testing.

The over-current relay is one of the easiest relays in a relay tech's repertoire, but if you lose your apprentice on the easy stuff then how will he or she learn the more difficult protective relays? 

While pages from only two modules are shown here there are four more modules that offer help with various curves.  

Zero Sequence Training Module

This module is so necessary that it is actually shown on the Price List as a Basic Module.

Do not confuse this with the Neutral Current (during switching) Training Module. This module introduces some complex ideas.

There is a review of PT's and CT's and a unique look at how hooking up your transformers in different modes can produce different values. This is a logical step into the next set of complex topics. 

Besides showing a review of PT's and CT's there is also the introduction to 3V0 and 3I0 "filters".

The industry uses these hook-up techniques to derive, from system values, the zero sequence quantities existing in the system.

Protective relays use the zero sequence voltage and current that appears as the indicator that a ground fault (or imbalance) is occurring.

Calculation of Symmetrical Components is covered in other advanced classes and documents but this is the advanced primer for things to come.