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 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
- Enter the initial configuration.
- Program the control Matrix.
- 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?
| 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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