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Relay Settings in the "Overcurrent" Room – Part 1

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As mentioned earlier, the first step in relay testing is entering the relay specifications into the software.

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To begin, we’ll first go over how to input the settings for a "Non-directional" relay.

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Start by opening the "General Test Object" window. From the "Device" block, enter the current transformer ratio, or "CT" ratio.

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Then, by double-clicking on the "Overcurrent" block, the "Overcurrent Protection Parameters" window will open,

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, where you can enter the relay settings. In the "Relay behavior" section, you’ll define the directionality

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of the protection function, the configuration of the "VT"s, and how the "CT"s are connected.

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 Since the relay we’re working with here is "Non-directional", select "Non-directional" in this window.

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Please note that the "VT Connection" and "CT Connection" options are only active when the relay is set to "Directional" mode.

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For "Non-directional" relays, these options will be disabled.

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In the "Tolerances" section, you can set the current and time tolerances for all relays,

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and the angle tolerance specifically for "Directional" relays.

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To set the current tolerance, enter the desired value as a percentage of the test current in the "Relative" field.

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As you can see, the default setting is 5%.

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You can also set the tolerance based on a multiple of the nominal "CT" current using the "Absolute" field,

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where the actual calculated value is displayed in the field next to it.

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Keep in mind, the software automatically selects the larger of the two defined tolerances when evaluating the characteristic curve.

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 For example, if the test current is set to 1 amp, a 5% tolerance results in a pickup range between

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0.95 amps and 1.05 amps

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. But if an absolute tolerance of 40 milliamps is used, the range would be between

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0.96 amps and 1.04 amps.

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. In this case, the software uses the larger range—between 0.95 and 1.05 amps

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as the effective tolerance. In the "Time" section, time tolerances can also be configured

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as either a percentage or a fixed value. For "Directional" relays, the angle tolerance is set in the "Angle" section.

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The “Compatibility” and “Other” sections were covered in the first video of the “Overcurrent” room. To define a characteristic curve, go to the "Elements" tab.

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In the "Element Name" column, you enter a name for the defined "Stages"—for example, here we’re naming it "Stage1".

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In the "Tripping Characteristic" column, you can select the type of characteristic curve.

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By default, it is set to "IEC Definite Time".

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To change the characteristic curve, either double-click on "IEC Definite Time", or click the three-dot icon

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in the "Characteristic" section to open the "Manage / Select Characteristic" window.

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. In the "Standard" section, you’ll find all the characteristic curves defined under the IEC standard.

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By selecting any of them, you can view its formula and coefficients in the "Characteristic" area.

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It’s important to make sure the curve selected here matches the characteristic curve that’s already configured in the relay.

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If the relay’s characteristic curve is not listed in this section,

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or if its coefficients differ from the formulas shown here, you’ll need to go to the "Predefined" folder.

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From there, look through the "Inverse", "I2T", "IAC", or "Reclosers" folders to find the curve formula that matches the relay and select it

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nIf the relay’s formula isn’t available in any of those folders, you can go to the "Custom" folder.

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By selecting "Custom Formula", you can enter the desired formula manually in the designated field,

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based on the provided coefficients, as well as the "Itest/Ipickup" and "Time Dial" values—marked as "M" and "Td".

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Once entered, just click "Save" and the formula will be ready to use.

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Additionally, if the relay’s characteristic curve is defined by a table of points, you can select "Table Example 2",

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then click "Copy to User Defined". After that, choose it from the "User Defined" folder

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and use the "Grabber" tool in the software to input the relay’s curve point by point.

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This way, you’ll be able to visualize the curve directly.

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This window and its functions will be explained in full detail in the upcoming videos.

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If the relay’s characteristic curve formula already exists in the software,

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but the coefficients used in it differ from those specified in the relay manual,

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you’ll need to select the desired formula, click on "Copy to User Defined", and then adjust the coefficients accordingly in the "User Defined" folder.

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For example, here we select the formula for the "Basler I2T-46N"

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" curve and copy it into the "User Defined" folder.

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Now, by selecting it, we can enter the required coefficients based on the relay manual.

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. After clicking "Save", the new curve with the updated coefficients will be stored in the software and ready for use.

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To continue, the "IEC Normal Inverse" curve is selected here.

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As you can see, in the "Elements" tab, a "Stage" of the type "IEC Normal Inverse" has been added.

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Now, in the "I Pick-up" column, the relay's pick-up current must be set as a multiple

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of the CT’s secondary rated current—here, it’s set to 1.1.

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You can also set the pick-up current using the "I Pick-up" field at the bottom of this tab. Once it’s configured,

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 its actual value will be displayed in the "Absolute" column.

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Next, in the "Time" column, the relay’s TMS—or "Time Dial" setting—is entered.

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This value can also be entered from the "Time Index" field at the bottom of the tab;

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; in this case, it’s set to 0.5.

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In the "Reset Ratio" column, the relay’s drop-out ratio is defined, which by default is set to 0.95

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And finally, in the "Direction" column, you’ll notice that this curve has been defined as "Non-Directional".