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How to Set a Schneider Electric's Sepam S20 Relay

The Author is a practicing electrical engineer and has executed multiple protection-coordination projects in his professional career.

The Sepam S20 Relay

The Sepam S20 Relay

The Schneider Electric's Sepam® Series S20 relay can be conveniently programmed using the SFT2841 configuration utility that is available from SE's website as a freeware.

This walk-through will assist you in setting and commissioning these relays for the various types of available fault protections using the SFT2841 utility.

Note: Values used in this article for insertion as fault parameters were determined after a proper protection coordination study. In case a protection coordination study is not available for your facility, feeder protection thumb rules can be used, which I will provide in the next article.

Steps to Commission a Sepam S20 Relay

  1. Enter the initial configuration.
  2. Program the control Matrix.
  3. Set parameters for respective fault functions.

The tutorial that follows below, elaborates each of these steps in every detail.

Which Fault Protections are Available in the S20 Relay?

The S20 relay offers protection against 5 basic faults.

ANSI CodeFault Name

50

Instantaneous Overcurrent / Short Circuit

51

Time Overcurrent

50N/G

Ground or Neutral Instantaneous Overcurrent / Earth Short Circuit

51N/G

Ground or Neutral Time Overcurrent / Earth Fault

46

Current Unbalance / Negative Sequence Fault

Entering the Initial Configuration

For the initial configuration you will need to specify the following parameters:

General characteristics screen.

General characteristics screen.

Parameters for initial configuration.

ParameterSpecification

Network Frequency

50 Hz or 60 Hz

Active Group Selection

Select which group of settings should be active. Sepam gives the option to set either group A or group B or both as active elements.

Remote Setting

Specify if the protection parameters need to accessed via remote link.

Language

English may be selected

CT Rating

Select the CT secondry rating, 1 A or 5 A

Number of CTs

Select for 3CTs or 2CTs

Rated Current

CT Primary Rating

Base Current

0.4 to 1.3 x Rated Current

Integration Period

5, 10, 15, 30, 60 mn (Select the minimum i.e 5)

Residual Current

Select 3I Sum if you have standard 3 Y-conncected CTs. This parameter specifies CT connection for measurement of 0-sequnce current by the relay.

Fault Recording Trigger

Number of periods which are recorded before the fault trigger (select the maximum).

Programming the Control Matrix for Sepam S20

The control matrix controls the activation of logic outputs and display LEDs in response to specific fault functions and input signals.

A typical configuration is shown below, which activates respective LEDs in response to each of the fault triggers.

Control matrix for Sepam S20

Control matrix for Sepam S20

Setting for 50/51 Phase Overcurrent Fault

The 50/51 phase over-current fault requires the parameters listed in the table below to be entered into the SFT2841 utility.

Phase over current fault configuration screen.

Phase over current fault configuration screen.

Parameters for 50/51 phase overcurrent fault.

ParameterSpecification

Element Activity

Set to 'On' for fault trigger to be activated for this type of fault.

Tripping Curve

Select the desired characterstic curve - Standard Inverse is selected in this case.

Threshold Current

This is the pick-up value of current for the fault trigger. 326 A in this case.

Delay

This is the value of time corresponding to the value of 10 x Threshold current on the tripping curve. In this case it is set at 0.3 s corresponding to a value of 10 x 326 A = 3260 A, also marked in the TCC below.

Timer Hold Curve

Select the curve for timer delay function (definite or IDMT).

Timer Hold Delay

If a 'coordination time delay' is required it can be entered here, in this case the delay function is bypassed.

Harmonic 2 Restraint

Can be checked to avoid nuisance tripping on transformer closure. If the 2nd harmonic is detected to be 17% or higher during transformer closure, relay maloperation is prevented.

Icc Current

Icc is the rated conditional short circuit current. It is the short circuit current that a circuit breaker assembly can withstand for its operating time. Since it depends on the C.B assembly, it is the same for all faults.

The parameters entered above, for both the phase over-current and short-circuit faults will result in the TCC plot given below, when the instantaneous and inverse-definite curves are integrated.

Typical standard inverse definite-time curve for the example relay settings demonstrated. The Inverse definite part and the instantaneous parts of the curve are integrated.

Typical standard inverse definite-time curve for the example relay settings demonstrated. The Inverse definite part and the instantaneous parts of the curve are integrated.

Setting for 50/51 - 2 Phase Short-circuit Fault

The 50/51 phase short-circuit fault requires the parameters listed in the table below to be entered into the SFT2841 utility.

Phase short-circuit fault configuration screen.

Phase short-circuit fault configuration screen.

Parameters for 50/51 - 2 phase short-circuit fault.

ParameterSpecifications

Tripping Curve

Select the desired characterstic curve - Definite Time is usually selected for short circuit protection.

Threshold Current

This is the pick-up value of current for the fault trigger. 6,800 A in this case.

Delay

This is the time that the relay holds after recieving a fault trigger for a short circuit fault. It is the Horizontal asymptote of the Instantaneous part of the TCC plot. In this case it is set at 0.07 s.

Timer Hold Curve

Select the curve for timer delay function (definite or IDMT).

Timer Hold Delay

If a 'coordination time delay' is required it can be entered here, in this case the delay function is bypassed.

Harmonic 2 Restraint

Can be checked to avoid nuisance tripping on transformer closure. If the 2nd harmonic is detected to be 17% or higher during transformer closure, relay maloperation is prevented.

Setting for 50N / 51N - 1 Earth Fault

The 50N/51N earth fault requires the parameters listed in the table below to be entered into the SFT2841 utility.

Earth fault configuration screen.

Earth fault configuration screen.

Parameters for 50N/51N earth fault.

ParameterSpecification

Tripping Curve

Select the desired characterstic curve - Standard Inverse is selected in this case.

Threshold Current

This is the pick-up value of current for the fault trigger. 40 A in this case.

Delay

This is the value of time corresponding to the value of 10 x Threshold current on the tripping curve. In this case it is set at 1.5 s corresponding to a value of 10 x 40 A = 400 A, also marked in the TCC below.

Timer Hold Curve

Select the curve for timer delay function (definite or IDMT).

Timer Hold Delay

If a 'coordination time delay' is required it can be entered here, in this case the delay function is bypassed.

Harmonic 2 Restraint

This can be activated to bypass the residual current when transformers are energized.

The parameters entered above, for both the earth and earth short-circuit faults will result in the TCC plot given below, where the instantaneous and inverse-definite curves are not integrated.

Typical standard inverse definite-time curve for the example earth fault relay settings demonstrated. The inverse definite part and the instantaneous parts of the curve are not integrated.

Typical standard inverse definite-time curve for the example earth fault relay settings demonstrated. The inverse definite part and the instantaneous parts of the curve are not integrated.

Setting for 50N / 51N - 2 Earth Short-circuit Fault

The 50N/51N earth short-circuit fault requires the parameters listed in the table below to be entered into the SFT2841 utility.

Earth short-circuit fault configuration screen.

Earth short-circuit fault configuration screen.

Parameters for 50N/51N - 2 earth short-circuit fault.

ParameterSpecification

Tripping Curve

Select the desired characterstic curve - Definite Time is usually selected for short circuit protection.

Threshold Current

This is the pick-up value of current for the fault trigger. 85 A in this case.

Delay

This is the time that the relay holds after recieving a fault trigger for a short circuit fault. It is the Horizontal asymptote of the Instantaneous part of the TCC plot. In this case it is set at 100 ms.

Timer Hold Curve

Select the curve for timer delay function (definite or IDMT).

Timer Hold Delay

If a 'coordination time delay' is required it can be entered here, in this case the delay function is bypassed.

Harmonic 2 Restraint

This can be activated to bypass the residual current when transformers are energized.

Setting for 46 - Negative Sequence Fault

The 46 negative sequence fault requires the parameters listed in the table below to be entered into the SFT2841 utility.

Negative sequence/Phase unbalance fault configuration screen.

Negative sequence/Phase unbalance fault configuration screen.

Parameters for 46 negative sequence fault.

ParameterSpecification

Select Curve

Select the desired characterstic curve - Definite Time is selected in this case.

Threshold Current

This is the pick-up value of current for the fault trigger.

Delay

This is the time that the relay holds after recieving a fault trigger for negetive sequence fault. In this case it is set at 300 ms.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

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