# RELAYS 101

### Relay Training Center Topics

There are numerous calculations that a good Relay Technician will do for their job, but in reality the majority of those calculations rely on Pythagorean's Theorum and some simple Trigonometry. Learn one thing well and apply it many times for your job. Load all of the files in this bundle into a single directory on your laptop (or to a DVD or to a USB). Most any modern browser can read and display the HTML as a webpage. For the pages that have math operations one will note that "Javascript" is used. Anyone versed in basic HTML and basic Javascript can modify these web pages if desired. Use a basic Text Editor. Specifically on the Relay Notes page, one can open the page (with your text editor) and ADD your own relay testing notes into the appropriate "textarea". If this technique is tried then be advised to use a simple text editor and SAVE the file as simple text (with the file extension "HTML"). Then re-open the file with your web browser and see your changes. While a fancy word processor can be used, it is known that these applications may add specialized formatting codes that simply do not work well within HTML. Please note the included applets are intended for training purposes. No calculations are guaranteed accurate.

Ohm's Law - The Beginning

Z=V/I Everyone's electrical education begins with Ohm's Law. This presentation is no different.

Polar to Rectangular Conversions

Polar to Rectangular Conversions allows you to enter horizontal and vertical coordinates and convert them to the equivalent polar quantity.

Power Triangle

Enter Watts and Vars values and calculate resultant Volt-Amps quantity. Or enter Volt-Amps quantity and calculate the value of the Watts and Vars

Zp To Zs Conversions

Enter any three values (from Zp, Zs, CTR and PTR) and calculate the fourth quantity.

Mho Math

Mho Math demonstrates the easy trigonometry used to predict the test values needed to produce a fault simulation that falls on the balance point (border) of a relay's characteristic curve if that curve is a mho circle.

Horizontal Characteristic

Horizontal Characteristic demonstrates the easy trigonometry used to predict the test values needed to produce a fault simulation that falls on the balance point (border) of a relay's characteristic curve if that curve is a horizontal characteristic.

Polar Plot On R-X Diagram

The R-X Diagram selection will let you enter Line Data and plot it on a quadrant diagram with a Mho Characteristic.

Calculate Phase-Phase Values

The Phase-to-Phase Calculation selection will let you enter Phase-to-Neutral values and calculate the resultant Phase-to-Phase values.

Subtract Vectors / Add Vectors

Subtract one vector from another in the first section. In the second section add up to eight vectors together (as might be necessary in a current differential scheme).

Calculate Symmetrical Components

Enter 3-phase values of either voltage, current or impedance (magnitudes and angles) and calculate the symmetrical components of those three sets of values.

B-C Fault with no V0

Demonstration of the voltage and phase angle action during a B-C fault. There is no V0 in a phase-to-phase fault.

Calculate K0

Calculate K0 where K0 = (Z0-Z1)/3Z1. This is the calculation used by some, though not all protective relay manufacturers. GE for example has used K0 = Z0/Z1.

In-Depth Instruction Learn K0 Calculation

Enter Line Impedance Data then predict the step-by-step values in the K0 calculation.

In-Depth Instruction Learn Zero Sequence Calculation

Enter 3-Phase System Values then predict (step-by-step) and calculate Zero Sequence Values.

In-Depth Instruction Learn Positive Sequence Calculation

Enter 3-Phase System Values then predict (step-by-step) and calculate Positive Sequence Values.

In-Depth Instruction Learn Negative Sequence Calculation

Enter 3-Phase System Values then predict (step=by-step) and calculate Negative Sequence Values.

In-Depth Instruction-Learn To Calculate Values For A Phase-Ground Relay Test

ZP-G = VP-G / IP-G It seems to be a bit complex but Ohm's Law makes accurate distance relaying possible. Step-by-step calculations to create an A-G simulated fault for relay testing.

In-Depth Instruction-Learn To Calculate Values For B-C Relay Test

ZP-P = VP-P / IP-P Ohm's Law with specific voltages and currents to calculate specific impedances. Step-by-step calculations to create a B-C simulated fault for relay testing. Note that this calculation will more accurately reflect the phase-to-phase fault that has no I0 and no V0.

In-Depth Instruction-Learn To Calculate Values For a 3-Phase Fault Relay Test

Z=V/I It's like Ohm's Law really does apply! Step-by-step calculations to create a 3-Phase simulated fault for relay testing.

Apparent Impedance - Calculate and Plot Line Fault Impedances

Z=V/I It's like Ohm's Law really does apply! Zp-g=Vp/(Ip+K0IN) and Zp-p=Vp-p/Ip-p. Calculations and R-X plots presented.

Relay Notes

General notes on relays and relay testing.

SEL One-Bus

The SEL One-Bus selection takes you to a Javascript translation of the original BASIC Programming Language routine written by SEL and distributed in their early distance relay instruction manuals.

Lecture Notes

Screen Shots of RELAYS 101 Lecture Notes

Lecture Notes Bus Diff

Screen Shots of RELAYS 101 Lecture Notes

Lecture Notes Assorted Calculations

Screen Shots of RELAYS 101 Lecture Notes