Cut Sheet

Page 3
SE-330HV Neutral-Grounding-Resistor Monitor Rev. 5-I-091115
2. OPERATION
2.1 S
ETTINGS
2.1.1 GF T
RIP TIME
GF TRIP TIME (definite time) is adjustable from 0.1 to
10.0 seconds. Time-coordinated ground-fault protection
requires this setting to be longer than the trip times of
downstream ground-fault devices.
A trip-time accumulator provides a ground-fault memory
function for detection of intermittent faults. The accumulated
time increases when a ground fault is detected and decreases
when a ground fault is not detected. A trip will eventually
occur when the time for fault current above the trip level is
greater than the time for fault current below the trip level.
2.1.2 GF T
RIP LEVEL
The SE-330HV uses a Discrete-Fourier Transform
(DFT) Algorithm to measure the fundamental component
of NGR current.
Choose an NGR let-through current and a ground-fault
trip level according to the guidelines in Section 1.1.
Set the ground-fault trip level as a percentage (2 to 100)
of the CT-primary rating. When the GF Trip Level is set
to MEM, the ground-fault setting stored in non-volatile
memory is used. This parameter must be set using a PC
running the SE-MON330 software connected to the USB
interface. The setting range is 2 to 100% of CT primary
rating in 1% increments. The default value is 15%. Inputs
are provided for 5-, 1-, and 0.05-A-secondary CT’s.
Typical values for 15-, 25-, and 100-A tripping systems
are shown in Table 1. Ground-fault trip levels for
selected CT’s are shown in Table 2. Refer to
the NGR Monitor Set-Point Assistant at
www.littelfuse.com/relayscontrols for other systems. The
Set-Point Assistant is included with the SE-MON330
software.
2.1.3 V
N
TRIP LEVEL
The SE-330HV uses a DFT algorithm to measure the
fundamental component of neutral voltage (V
N
).
If neutral voltage is greater than the V
N
TRIP LEVEL
setting for the duration of the resistor-fault trip time and
ground-fault current is less than 5% of the CT rating, the
SE-330HV will trip on resistor fault. If the resistor-fault
circuit is tripped and the neutral voltage exceeds the V
N
TRIP LEVEL setting for an interval greater than the GF
TRIP TIME setting, the ground-fault circuit will also trip.
The V
N
TRIP LEVEL range is 100 to 10,000 V with
switch S5 in the 100-k (Vx1) position, and the range is
200 to 20,000 V with switch S5 in the 200-k (Vx2)
position. Calculate the voltage across the NGR when
NGR current is equal to the pick-up current of the ground-
fault circuit. Set the V
N
TRIP LEVEL at the next largest
value. See Fig. 1 and Section 2.1.4.4.
Typical values for 15-, 25- and 100-A tripping systems
are shown in Table 1. Refer to the NGR Monitor Set-
Point Assistant at www.littelfuse.com/relayscontrols for
other systems.
N
OTE: A resistor-fault trip is held off if the ground-fault
current is above 5% of the CT rating.
2.1.4 CONFIGURATION SETTINGS
Eight configuration switches (S1 to S8) and a
calibration button are located behind the access cover on
the front panel. See Fig. 1.
CAL
CALIBRATION BUTTON
SPARE
S1
FAIL-SAFE
LATCHING GF TRIP
LATCHING RF TRIP
200 kΩ
50 Hz
SPARE
RUN
NOTE: DEFAULT SETTINGS SHOWN.
S2
S3
S4
S5
S6
S7
S8
NON-FAIL-SAFE
NON-LATCHING GF TRIP
NON-LATCHING RF TRIP
100 kΩ
60 Hz
UPGRADE
FIGURE 1. Configuration Switches.
2.1.4.1 T
RIP-RELAY MODE AND TRIP-MEMORY
MODE (S2)
Set switch S2 to select the operating mode of trip relay
K1. In the non-fail-safe mode, relay K1 energizes and its
contact closes when a trip occurs. The non-fail-safe mode
can be used to trip shunt-trip circuit breakers. In the non-
fail-safe mode, SE-330HV trips are reset when supply
voltage is cycled.
In the fail-safe mode, relay K1 energizes and its contact
closes if there are no trips. Contacts open if there is a trip, a
loss of supply voltage, or a processor failure. In the fail-safe
mode, SE-330HV trips are not reset when supply voltage is
cycled.
N
OTE: Switch S2 does not affect the operating modes of
relays K2, K3, and K4.
2.1.4.2 G
ROUND-FAULT-TRIP LATCH (S3)
Set switch S3 to select latching or non-latching ground-
fault-circuit operation. Non-latching operation defeats
ground-fault trip-memory. See Section 2.3.
2.1.4.3 R
ESISTOR-FAULT-TRIP LATCH (S4)
Set switch S4 to select latching or non-latching resistor-
fault-circuit operation. Non-latching operation defeats
resistor-fault trip-memory. See Section 2.3
2.1.4.4 S
ENSING-RESISTOR SELECTION (S5)
Set switch S5 to the resistance of the sensing resistor. For
the ER-15KV, ER-25KV, and ER-35KV, select 100 k.
For the ER-1000HV and ER-72KV, select 200 k. Switch