Current Sensing

4.1.1. Description

This Setting group is critical for all over-current protection features that have settings specified in multiples of CT rating. When the relay is ordered, the phase, ground, and sensitive ground CT inputs must be specified as 1 Amp.

As the phase CTs are connected in wye (star), the calculated phasor sum of the three phase currents (Ia + Ib + Ic = Neutral Current = 3 I0) is used as the input for the neutral over-current. In addition, a zero-sequence (core balance) CT which senses current in all of the circuit primary conductors, or a CT in a neutral grounding conductor may also be used. For this configuration, the ground CT primary rating must be entered. To detect low level ground fault currents, the sensitive earth input may be used. In this case, the sensitive ground CT primary rating must be entered.

For additional details on CT connections, refer to (see 10.12. Current Inputs Wiring Diagram).

4.1.2. Setting

PRIMARY SETTING / SYSTEM SETUP / CURRENT SENSING / PHA CT Ratio

Range 1 ~ 1200

Default 1000 Step 1

Enter the phase CT primary current value. [CURRENT SENSING]

>PHA CT Ratio: 1000 GND CT Ratio: 1000 SEF CT Ratio: 1000

PRIMARY SETTING / SYSTEM SETUP / CURRENT SENSING / GND CT Ratio

Range 1 ~ 1200

Default 1000 Step 1

Enter the ground CT primary current value.

PRIMARY SETTING / SYSTEM SETUP / CURRENT SENSING / SEF CT Ratio

Range 1 ~ 1200

Default 1000 Step 1

Enter the sensitive earth CT primary current value.

4.2. Line VT Sensing

4.2.1. Description

To measure Source Voltage, set Connect Type, 2ndNominal Voltage, VT Ratio.

With Line VTs installed, the EVRC2A can be used to perform voltage measurements, power calculations, and directional control of over-current elements.

4.2.2. Setting

PRIMARY SETTING / SYSTEM SETUP / LINE VT SENSING / Connect Type

Range NONE, WYE, DELTA, CVD-W, CVD-D

Default NONE Step ~

Enter None if line VTs are not to be used.

NONE : VT uninstalled.

If used, external PT by user, enter the VT connection made to the system as Wye or Delta.

WYE : Install type wye. DELTA : Install type delta.

If installed VT of Capacitor Voltage Divide type.

CVD-W : If the user system made to 3 phase 4 wire.

[LINE VT SENSING] >Connect Type: NONE VT 2nd(v): 100.0 VT Ratio: 86.6 [CURRENT SENSING] PHA CT Ratio: 1000 GND CT Ratio: 1000 >SEF CT Ratio: 1000 [CURRENT SENSING] PHA CT Ratio: 1000 >GND CT Ratio: 1000 SEF CT Ratio: 1000

PRIMARY SETTING / SYSTEM SETUP / LINE VT SENSING / VT 2nd(v)

Range 50.0 ~ 250.0

Default 100.0 Step 0.1

Enter Secondary Nominal Voltage(V)

This setting is the voltage across the VT secondary winding when nominal voltage is applied to the primary.

PRIMARY SETTING / SYSTEM SETUP / LINE VT SENSING / VT Ratio

Range 10.0 ~ 760.0

Default 86.6 Step 0.1

Enter the VT primary to secondary turns-ratio with this setting.

4.2.3. Setting Examples

Use of CVD

Case of CVD installed in Recloser, setup as follows;

Usable in Wye connection. Set VT2nd(v) 100 as Default. PT Ratio is calculated as below.

VoltageФ-Ф = VoltageФ-N × SQRT(3) VoltageФ-N = VT 2nd(v) × VT Ratio

Hence,

15㎸Ф-Ф = 8.66㎸Ф-N, therefore 8.66㎸Ф-N = 100(V) × 86.6

If user line voltage between phases (VoltageФ-Ф) is 11, set VT2nd(v) of 73.3V and set VT Ratio of 86.6 (11㎸Ф-Ф => 6.35㎸Ф-N, 6.35㎸ = 73.3(V) × 86.6)

27㎸Ф-Ф = 15.59㎸Ф-N, therefore 15.59㎸Ф-N = 100(V) × 155.9 38㎸Ф-Ф = 21.94㎸Ф-N, therefore 21.94㎸Ф-N = 100(V) × 219.4

[LINE VT SENSING] Connect Type: NONE VT 2nd(v): 100.0 >VT Ratio: 86.6 [LINE VT SENSING] Connect Type: NONE >VT 2nd(v): 100.0 VT Ratio: 86.6

Use of External PT by User

Line is Wye connection type and has VФ-Ф = 15㎸. If external rated PT is 14400 : 120, then VT Ratio is 14400/120. Because of 15㎸Ф-Ф = 8.66㎸Ф-N, VT2nd(v) is 8.66㎸Ф-N / 120 = 71.2V

Line with Delta connection type and has VФ-Ф= 15㎸. If external rated PT is 14400 : 120, then VT Ratio is 14400/120 and VT2nd(v) is 15㎸Ф-Ф / 120 = 125V

Table 4-1. VT Ratios of External PTs

Capacitor Voltage Divider Potential Transformer

Wye connection Wye connection Delta connection Line-Line

Voltage

VT 2nd (v) VT Ratio VT 2nd (v) VT Ratio VT 2nd (v) VT Ratio

15㎸ 100 86.6 71.2 120 (14400:120) 125 120 (14400:120) 27㎸ 100 155.9 72.5 215 (25800:120) 125.6 215 (25800:120) 38㎸ 100 219.4 73.1 300 (36000:120) 126.7 300 (36000:120)

4.3. Line VL Sensing

4.3.1. Description

To measure Load Voltage, set Connect Type, 2ndNominal Voltage, VT Ratio.

With Line VLs installed, the EVRC2A can be used to perform synchronism elements.

4.3.2. Setting

PRIMARY SETTING / SYSTEM SETUP / LINE VL SENSING / Connect Type

Range NONE, WYE, DELTA, CVD-W, CVD-D

Default NONE Step ~

Enter None if line VLs are not to be used.

NONE : VL uninstalled.

If used, external PT by user, enter the VL connection made to the system as Wye or Delta.

WYE : Install type wye. DELTA : Install type delta.

If installed VT of Capacitor Voltage Divide type.

CVD-W : If the user system made to 3 phase 4 wire. CVD-D : If the user system made to 3 phase 3 wire.

PRIMARY SETTING / SYSTEM SETUP / LINE VL SENSING / VL 2nd(v)

Range 50.0 ~ 250.0

Default 100.0 Step 0.1

Enter Secondary Nominal Voltage(V)

This setting is the voltage across the VL secondary winding when nominal voltage is applied to the primary.

PRIMARY SETTING / SYSTEM SETUP / LINE VL SENSING / VL Ratio

Range 10.0 ~ 760.0

Default 86.6 Step 0.1

Enter the VL primary to secondary turns-ratio with this setting. [LINE VL SENSING]

>Connect Type: NONE VL 2nd(v): 100.0 VL Ratio: 86.6

[LINE VL SENSING] Connect Type: NONE VL 2nd(v): 100.0 >VL Ratio: 86.6 [LINE VL SENSING] Connect Type: NONE >VL 2nd(v): 100.0 VL Ratio: 86.6

4.4. System Power

4.4.1. Description

Menu to set Frequency of Protected Line and installed Phase rotation.

4.4.2. Setting

PRIMARY SETTING / SYSTEM SETUP / SYSTEM POWER / Frequency

Range 50, 60㎐

Default 50㎐ Step ~

Select the nominal power system frequency. This value is used as a default to set the optimal digital sampling rate.

PRIMARY SETTING / SYSTEM SETUP / SYSTEM POWER / Phase Rotation

Range ABC, ACB

Default ABC Step ~

Select the phase rotation of the power system.