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 Schneider Electric's Sepam Series S20 relay can be conveniently programmed using the SFT2841 configuration utility that is available from SE's website as freeware.
This walkthrough 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
- Enter the initial configuration.
- Program the control Matrix.
- Set parameters for respective fault functions.
The tutorial that follows below elaborates on each of these steps in every detail.
Which Fault Protections Are Available in the S20 Relay?
| ANSI Code | Fault 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.
| Parameter | Specification |
|---|---|
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
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.
| Parameter | Specification |
|---|---|
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.
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.
| Parameter | Specifications |
|---|---|
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.
| Parameter | Specification |
|---|---|
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.
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.
| Parameter | Specification |
|---|---|
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.
| Parameter | Specification |
|---|---|
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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