How to Set a Schneider Electric's Sepam S20 Relay
The Schneider Electric Company offers the Sepam® Series S20 relay as its mainstream protection relay for most common applications such as feeder, bus bar and substation protection.
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
|
These relays 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.
Initial Configuration
For the initial configuration you will need to specify the following parameters:
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).
|
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.
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.
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.
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.
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.
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.
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.
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.
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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