1. GROUND FAULT & EARTH LEAKAGE MONITORS
SE-700 SERIES
GROUND FAULT
&
EARTH LEAKAGE MONITORS
This presentation presupposes audience familiarity with ground-fault basics.
Startco Engineering is a leader in the field of ground-fault monitoring. Many of our protection relays, including Neutral Grounding Resistor Monitors, Motor Protection Units, and Ground-Fault Ground-Check Monitors, incorporate ground-fault monitoring.
This presentation is about the SE-701, a purpose-built ground-fault monitor.

2. THE SE-700 FAMILY
The SE-700 series are microprocessor-based earth-leakage monitors for impedance-grounded and solidly grounded systems. The SE-700’s detect earth-leakage current using a zero-sequence core-balance current transformer, and will trip on the selected level of zero-sequence current after the selected time delay.

3. THE SE-700 FAMILY: SE-701, SE-703, SE-704

4. SE-700 FAMILY FEATURES Fixed frequency or variable frequency
Harmonic filtering (DFT)
Fail-safe / non-fail-safe output operation
Isolated trip contacts
Signal input: Core-balance CT
Open-CT detection
Supply: 120 Vac, 240 Vac, 24 Vac,
120/240 Vac, 55 to 275 Vac and 75 to
275 Vdc, 9 to 36 Vdc, and 30 to 70 Vdc
0 - 5 Vdc analog output
Mechanical-flag and LED trip indication
Self-test feature
Remote reset input
Surface mount / DIN rail mount /
optional panel mount
To mount use two screws, snap onto a DIN rail, or panel mount with the optional PMA-55 kit (shown on upcoming slide).
Fail Safe operation energises the relay contacts when the unit is not tripped. Hence the unit is in the tripped state when control power is lost. In non-fail-safe operation the relay contacts are energised only in the tripped state.
Trip Inhibit, when activated, will not allow a trip when ground-fault current exceeds 11 times the CT-primary rating. This protects the circuit breaking device that the SE-701 is controlling by preventing it from clearing a fault much larger than it was designed to handle. This type of fault is a high level fault and should be cleared by overcurrent devices such as fuses or circuit breakers.
The sensing device used to provide input to the SE-701 is a current transformer (CT). This can be a standard 1 Amp or 5 Amp secondary CT, or a sensitive nickel-core 5 Amp primary CT (EFCT-1 or EFCT-2). See CT selection chart.
The SE-701 tolerates wide fluctuations in control power. The 120 V unit tolerates 72 to 138 Vac. The 240 V unit tolerates 144 to 276 Vac.
Analog output indicates ground-fault current sensed by the CT. Output is 5 V when sensed current is 100% of the CT-primary rating. This output can be used to help trace the location of ground faults in a pulsing GF system.Normally-Open and Normally-Closed form Z contacts are provided. Form Z contacts are isolated. This allows, say, 120 Vac at one and 24 Vdc at the other. Their operation depends upon the choice of Failsafe or Non-Failsafe mode. The output relay rating is 8 A resistive, 250 Vac / 30 Vdc.

5. SE-701 FACE-PLATE FUNCTIONS
INHB: LED indicates trip inhibit function active
TRIP: LED trip indication
PWR: Power on LED
TRIP: Mechanical-flag trip indication
% CT PRIMARY: Selectable ground-fault trip level as a % of CT primary rating
TIME: Trip time can be set from 0.05 to 2.5 s
The TEST button, when pressed for 1 second, causes the ground-fault circuit to trip, activates ground-fault indication, and operates the output relay. The one second delay is to prevent accidental, nuisance operation.
Ground-Fault-Current Trip Level can be set from 1% to 99% of the CT-primary rating. For example if you have a 100:5 CT, the unit can be set to trip (or alarm) at settings between 1 A and 99 A in one amp increments. It should be set substantially below prospective ground-fault current. To avoid sympathetic tripping, the trip level must be above the system charging current.
The Power On LED lights when supply power is applied
Trip Inhibit lights when the output relay operation was inhibited during a high-current ground-fault (when enabled).. Reset when ground-fault trip is reset.
Trip LED lights and trip flag flips to indicate a ground-fault trip. The LED flashes to indicate a CT-fault trip. The fluorescent flag remains flipped if supply power is removed. It is not reset by cycling the supply power. It is reset only by operating the reset circuit (front panel or remote).
Trip time can be set at one of ten levels from 50 ms to 2.5 s. This switch is used to co-ordinate trip times of ground-fault devices in the system. This is to minimize the amount of equipment taken out of service in response to a ground-fault.
A Trip remains latched until the RESET button is pressed (or the remote reset is pressed, or supply voltage is cycled). The reset circuit responds only to a single shot input, so a jammed RESET button or a shorted switch will not maintain a reset signal.
TEST: Causes ground-fault circuit to trip
RESET: Resets trip after fault is cleared

6. SE-701 SELECTABLE FEATURES
AUTO RESET
VARIABLE FREQ
CT VERIFY ON
INHIBIT ON
NON-FAIL-SAFE
LATCHING
FIXED FREQENCY
CT VERIFY OFF
INHIBIT OFF
FAIL-SAFE 5 4 3 2 1
Dead-front self-locking screw / clamp connectors
1-A CT Input
5-A CT Input
EFCT Input
Three dip switches are located beneath the hermetic cap located on top of the SE The switches allow selection of: CT Verify On / Off
Inhibit On / Off (Class II / I)
Fail-Safe / Non-Fail-Safe
Note the dead-front screw/clamp connectors (14 AWG).

7. SE-703: DESIGNED FOR AUSTRALIA’S MINING INDUSTRY
Two-second power-loss
hold-up time
Sensitive protection without
nuisance trips
CT Verification and CT-loss
trip
SAA-AS2081 compliant

8. SE-703 FACE PLATE CT: CT Verification LED TRIP: LED trip indication
PWR: Power on LED
TRIP: Mechanical-flag trip indication
LEVEL: Selectable ground-fault trip level—75 mA to 1000 mA
TIME: Trip time can be set from 55 ms to 500 ms
TEST: Causes ground-fault circuit to trip
RESET: Resets trip after fault is cleared

9. SE-703 SELECTABLE FEATURES
CT VERIFY ON
VARIABLE FREQ
NON-FAIL-SAFE
CT VERIFY OFF
FIXED FREQENCY
FAIL-SAFE 3 2 1
EFCT Input
Dead-front self-locking screw / clamp connectors

10. SE-704 FACEPLATE CT: CT Verification LED TRIP: LED trip indication
PWR: Power on LED
TRIP: Mechanical-flag trip indication
LEVEL: Selectable ground-fault trip level—10 mA to 500 mA
TIME: Trip time can be set from 30 ms to 1000 ms
TEST: Causes ground-fault circuit to trip
RESET: Resets trip after fault is cleared

11. SE-704 SELECTABLE FEATURES
AUTO RESET
CT VERIFY ON
VARIABLE FREQ
NON-FAIL-SAFE
LATCHING
CT VERIFY OFF
FIXED FREQENCY
FAIL-SAFE 4 3 2 1
SE-CS30 Input
Dead-front self-locking screw / clamp connectors

12. PMA-55 PANEL MOUNT ADAPTER
The PMA-55 panel mount adapter is used to bring the SE-701 to the front door of an enclosure. The PMA-55 is used in applications in which trip time and/or trip current set points must be operator accessible.
The SE-701 is DIN rail mounted to the PMA-55 bracket. The bracket’s bezel conceals and protects the dead-front terminals, after installation. Ie: removing the bezel does not dismount the PMA-55.

13. SE-700 SECURITY FEATURE
Remove the set-point selection knobs to make unauthorized adjustments more difficult

14. GROUND-FAULT CT SELECTION CHART
EFCT & FLUX
CONDITIONER
2.75” or 5.50” ID’s
START
IT>5A, or
IP >100 A, or
IS > 2.5 kA
Note 1
YES NO
ECONOMY
PERFORMANCE
IT < 0.5 A
IS > 1 kA
Note 2
IS < 5 kA
IS < 8 kA
MODEL 130 CT
5.75” ID
Note 3
MODEL 120 CT
5.75” ID
MODEL 170 CT
4.25” ID
EFCT-1: 3.23” ID or
EFCT-2: 6.10” ID
IT : Ground-Fault Trip or Alarm Level
IP : Prospective Ground-Fault Current
IS : Surge Current (1.6 x LRA for motors)
Note 1: IP > 800 A for MPU-16A.
Note 2: Symmetrically locating phase conductors in the center of the CT
window will reduce CT saturation and increase the surge-current limit.
Note 3: If IT < 5 A, use a 500:5 or 100:1 CT and the EFCT input.
If IP > 70 A, also use a SE-EFVC voltage clamp.
Applies to:
SE-701, MPU-16A,
MPS & FPU-16
Use this selection flow chart to determine which ground-fault CT is appropriate for a given application. Basic information requrired is: ground-fault trip (or alarm) level, prospective ground-fault current, system surge current.
Example:
An SE-701 is monitoring a circuit with several motors with a total locked-rotor current of 1500 A. The supply transformer has a 25 A neutral grounding resistor (NGR). We want the SE-701 to trip on 100 mA ground-fault current.
Beginning at START and moving right to the first decision block of the flowchart we see that ground-fault current trip level, IT, at 100 mA is less than 5A; prospective ground fault current, IP, at 25 A is less than 100 A; surge current, IS, at 1.6 x 1500 A = 2400 A is less than 2500 A. Therefore, we move down one level in the flowchart into another decision block. Again, IT, at 100mA is less than 500 mA so we move down one more level of the flowchart. Here we see that an EFCT earth fault current transformer with a flux conditioner is required. All that is left to decide is the CT window diameter. This is a function of phase cable size.
The flux conditioner provides a low resistance path for magnetic flux. The result is elimination of local saturation of the CT—eliminating nuisance tripping due to this local saturation.
The criterea for the decision between performance and economy CT’s are price and the possible future requirement for sensitive ground-fault current detection.

15. LOCATING PHASE CONDUCTORS IN A ZERO-SEQUENCE-CT WINDOW
GAP A B C
SPACER
FLUX
CONDITIONER
An ideal window-type current transformer (CT) responds only to the sum of the currents flowing through its window; however, an actual CT may saturate if the phase currents are too large. This results in CT output even if the sum of the phase currents is zero. Saturation can be minimized by choosing a CT with an adequate core and symmetrically locating the phase conductors in the centre of the CT window. Use of a flux conditioner can eliminate local saturation. The right-hand figure includes a flux conditioner.
If shields,drain,ground, or ground-check wires pass through the CT, return them through the CT before termination.
Firmly secure the conductors in the centre of the CT window so they cannot be moved accidentally or under fault conditions.
The gap between the conductors and the CT should be at least 12.7 mm (0.5 in). It is preferable to have a gap of 25.4 mm (1.0 in) or more.
For multiple conductors per phase, arrange the conductors as shown in the figure. A spacer with the same diameter as the conductors should be used to separate phase conductors.
Symmetrically locate the phase conductors in the CT window
The gap between the conductors and the CT should be at least 12.7 mm (0.5 in)
It is preferable to have a gap of 25.4 mm (1 in) or more

16. SE-701 TYPICAL APPLICATIONv
REMOTE RESET
ANALOG OUTPUT
+24Vdc
0 V
GROUND-FAULT INDICATION
TO PLC INPUT
STOP
START 1M
O/L
SAWMILL L N
CURRENT TRANSFORMER
This typical SE-701 circuit diagram shows: 5 A secondary CT input, a control transformer across load-side supply phases, a 110 Vac contactor controlled by momentary start switch in series with the fail-safe SE-701 output relay contacts, a 24 Vdc remote trip indicator light in parallel with a PLC input, a remote reset normally open switch, and a voltmeter connection to the analog output.