When conducting line protection tests, the operation of the line protection under various fault point conditions of the line is usually simulated, with little attention paid to the action area of the line protection in the complex plane, namely the impedance characteristic circle (characteristic polygon) of the distance relay. This article introduces how to search the impedance characteristic circle of the NR Electric RCS-931 Line Protection Device by using the impedance characteristic test interface of the Relaystar-S60 Handheld Relay Protection Test System.

1 Protection-Related Settings

(1) Setting of Protection Fixed Value Control Words

No.	Setting Name	Value	No.	Setting Name	Value
01	Phase-to-Phase Distance Zone I Setting	2.0Ω	02	Phase-to-Phase Distance Zone II Setting	4.0Ω
03	Phase-to-Phase Distance Zone II Time	0.5s	04	Phase-to-Phase Distance Zone III Setting	6.0Ω
05	Phase-to-Phase Distance Zone III Time	1.0s	06	Earth Distance Zone I Setting	2.0Ω
07	Earth Distance Zone II Setting	4.0Ω	08	Earth Distance Zone II Time	0.5s
09	Earth Distance Zone III Setting	6.0Ω	10	Earth Distance Zone III Time	1.0s
11	Zero-Sequence Compensation Coefficient	0.67	12	Positive Sequence Sensitive Angle	78°
13	Enable Phase-to-Phase Distance Zone I	1	14	Enable Phase-to-Phase Distance Zone II	1
15	Enable Phase-to-Phase Distance Zone III	0	16	Enable Earth Distance Zone I	0
17	Enable Earth Distance Zone II	0	18	Enable Earth Distance Zone III	0
19	Enable Auto-Reclosing	0

 

(2) Setting of Protection Press Plates

In the Press Plate Settings, set "Distance Protection Press Plate Input" to "1", "Zero-Sequence Protection Press Plate Input" to "1", and "Differential Protection Press Plate Input" to "0".

For the control words, only set "Phase-to-Phase Distance Zone II Input" to "1", and set all other control words to "0".

On the protection panel, close the hard press plate for Distance Protection and the hard press plate for Zero-Sequence Protection.

2 Test Wiring

△ RCS-931 Distance Protection and Auto-Reclosing Wiring Diagram

Connect the voltage output terminals Ua, Ub, Uc, Un of the Relaystar-S60 to the AC voltage terminals Ua, Ub, Uc, Un of the protection device respectively.

Connect the current output terminals Ia, Ib, Ic of the Relaystar-S60 to the AC current polar terminals (IA, IB, IC) of the protection device respectively; short-circuit the AC current non-polar terminals (IA', IB', IC') of the protection device and connect them to the zero-sequence current polar terminal (IN), and finally connect back to the current output terminal In of the Relaystar-S60 from the zero-sequence current non-polar terminal (IN').

Connect the input contact A of the Relaystar-S60 to the phase-separated trip output contact Trip A of the protection device, and connect the +KM terminal of the Relaystar-S60 to the common terminal of the protection device.

The switch position corresponding to the line here is "Closed Position", and the output wiring is not considered.

3 Calibration of Impedance Characteristic Circle Function

In the Impedance Characteristic Test menu, select Search Impedance Boundary, set the search mode to Bidirectional Search and the resolution to 0.05. The specific parameter settings are as follows.

1. Parameter Setting for "Impedance Boundary Search" Test

△ Test Item Parameter Setting

Select ABC three-phase short circuit fault as the fault type.

Select Constant Current as the calculation model.

Set the pre-fault delay to 12s (it is recommended to ensure PT disconnection recovery and device reset under each state).

Set the maximum fault time to 1s (it shall be 0.5s longer than the Distance Zone II time to meet the requirement).

The zero-sequence compensation coefficient is not required to be set for the three-phase short circuit mode.

Keep the remaining parameters as default values.

△ Impedance Boundary Search Parameter Setting Interface

Set the search center to half of the setting value, i.e., 2Ω, and the positive sequence impedance angle to 78°.

Set the search radius to 3Ω (it shall be larger than half of the setting value).

The angle step determines the number of search points: a smaller step means more search points, higher precision and longer time consumption; a larger step means fewer search points, relatively lower precision and shorter time consumption. It is recommended to set the step to 30° and the number of search lines to 12.

△ Search Setting Parameter Setting Interface

Set the fixed values here and select Circle Characteristic; observe the boundary curve in the impedance boundary diagram on the right after filling in the parameters.

The solid circle represents the theoretical characteristic circle, and the dashed circle represents the 10% error range.

(2) Test Operation Method

Click the Start button to start the output of the Relaystar-S60; the tester first outputs the no-load state, then the fault state until the protection trips reliably.

The input contact collects the action time, and the Relaystar-S60 automatically proceeds with subsequent tests until all protection tests are completed and the test ends automatically.

Select whether to save the test results according to the prompt.

(3) Test Results

The input quantity records the test action information after the test is completed.

△ Protection Action Test Interface

△ Impedance Characteristic Circle of the Protection Device

The Relaystar-S60 automatically records the test result data of the impedance characteristic test, as shown in the table below:

Test Conclusion

The action status and action time information of the distance protection, as well as the action characteristic circle of the impedance characteristic protection, are viewed through the test report. The impedance error range is all within 10%, which meets the functional application requirements.