Load Protection Module

(PS - 005)

Preventing induction motor from rotating under no-load
Under-power Overcurrent Protection of a Three-Phase Induction Motor
Asymmetric voltage unbalance protection for three phase induction
Prohibiting motor reverse rotation

Load Protection Module (PS - 005)

Digital content (BI-01)

Three-phase Complex Load Module (PS-001.5)

In the design of electrical power systems, the ANSI Standard Device Numbers ANSI/IEEE Standard denote what features a protective device supports such as a relay or circuit breaker. These types of devices protect electrical systems and components from damage when an unwanted event occurs, such as an electrical fault. Device numbers are used to identify the functions of devices. This module introduces trainees to ways of protection of different types of loads (static & dynamics). It is connected before Loads Module and after Step Down Substation Protection Module.

Phase under voltage protection (ANSI Standard: 27P)
Power factor / under power protection (ANSI Standard: 37P)
Phase inversion protection (ANSI Standard: 47)
Thermal overload protection (ANSI Standard: 49)
Non-directional instantaneous overcurrent protection (ANSI Standard: 50P)
Phase over-voltage protection (ANSI Standard: 59P)

Continuously monitors the three-phase output voltage of synchronous generator to warn against under-voltage condition during synchronization process
If measured voltage moves below the set point limit, the relay contacts will change-over after the selected “Delay-OFF” has elapsed, giving an alarm or initiation signal.
If voltage measured exceeds threshold (set point), the relay contacts will return to original state only after the reset time (“Delay-ON”) has elapsed.
Can be used in 3-wire and 4-wire network
Offers user adjustable trip point (set point) and time delay settings.
The set point adjustment for under-voltage is in the range of 25%
As soon as the monitored signal moves outside of the set point limit, the time delay is activated, after which a trip will occur. The time delay prevents the relay from tripping for a predetermined period to prevent nuisance tripping.
The relay is automatically reset once the monitored voltage rises above the set point.
Adjustable off-delay: 0.1 …20sec
Adjustable reset-delay: 0.1…20sec
Adjustable under-voltage trigger range: 70% …95% (corresponding to 270V…370V AC)
LED indicators for relay activation during under-voltage condition
Relay output: Single change-over contact
Contact rating: 250V AC, 8A

Load monitoring relay for under-power, over-power or window
Works in 1-phase and 3-phase networks
The operating states are indicated using colored LEDs:
- «U/t» LED: Supply voltage and starting override
- «MAX» LED: Upper threshold value
- «MIN» LED: Lower threshold value
- «I=0» LED: Load switched off
- «REL» LED: Output relay
Mode of operation can be chosen using «FUNCTION» rotary switch
Set of potentiometers to adjust:
- Response delay
- Lower threshold power factor value
- Upper threshold power factor value
- Starting override
Adjustable starting override: 1…100sec
Adjustable response delay: 0.1…40sec
Input current range: 0.5…10A AC
Max switching threshold P.F: 0.2 to 1
Min switching threshold P.F: 0.1 to 0.99
Operating voltage: 415V AC
If the measured power factor exceeds the value set at the «MAX» controller, the set response delay (DELAY) starts (red «MAX» LED flashes). After the delay time has elapsed (red «MAX» LED is ON), output relay «R» drops out (yellow «REL» LED is OFF).
If the measured power factor falls below the value set at the «MIN» controller (red «MAX» LED is OFF), output relay «R» picks up again (yellow «REL» LED is ON).
If the error memory has been activated (OVER + LATCH) and the measured power factor has exceeded the value set at the «MAX» controller for longer than the set response delay, output relay «R» does not pick up if the power factor falls below the value set at the «MIN» controller. Once the error has been reset, output relay «R» picks up when the supply voltage is applied again and the measuring cycle starts again once the set starting override (START) has elapsed.
Relay output: 2x changeover contacts
Contact ratings: 250V-3A (AC)

Phase Sequence Relay monitors the order of 3 phases feeding motors.
If R,S and T phases are in correct order, ON LED on the front panel is turned on.
If the phase order is wrong, ON LED is turned off and the output relay is switched to OFF.
Relay output: Single change-over switch
Contact rating: 250V AC, 8A (resistive)

Differential thermal overload relay
Phase failure sensitive
Reset mode can either be manual or automatic.
Pushbutton for simulating relay tripping
Pushbutton for “Stop” and manual Reset
Trip flag indicating overload relay tripped.
Rated operational voltage: 0…400V AC
Thermal protection adjustment range: 1.6A…2.5A AC
Phase failure sensitivity tripping current: 130 % of “In” on two phase, the last phase at 0 current or 30 % of “In” on one phase, the others at “In”.
Auxiliary contact: 1 NO + 1 NC
Tripping threshold: (1.14 +/- 0.06) x In

This combined short circuit and over-current relay is applied for protection of generators against both over-currents and short circuit currents (I> and I>>).
The relay measures the highest of the 3- phase currents, providing an RMS measurement at sinusoidal currents.
The measurement is based on average values for I>, peak values for I>>
The set point values are set on the front of the relays by means of potentiometers.
If a current exceeds a set point, the output is activated.
If exceeded, a fault signal is generated, and the associated yellow LED is lit.
Measurement of 3-phase currents
LED indication of fault condition
Timer-controlled tripping
LED indication for activated relay
When the set point is exceeded, its timer starts and will run as long as the fault condition prevails.
If the fault disappears, the timer is reset. When the timer expires, the contact is activated and the associated red LED is lit.
Short circuit current setting: 1.0 to 4.0 × In
Tripping delay time for short-circuit current: 0 to 1sec
Over-current setting: 0.5 to 1.5 × In
Tripping delay time for over-current: 0 to 20sec
Number of contacts: Single change-over switch per relay type
Contact ratings: 250 V AC/24 V DC, 8 A (200,000 change-overs at resistive load)

Continuously monitors the three-phase output voltage of synchronous generator to warn against over-voltage condition to warn against over-excitation condition
If measured voltage moves above the set point limit, the relay contacts will change-over after the selected “Delay-OFF” has elapsed, giving an alarm or initiation signal.
If voltage measured falls below threshold (set point), the relay contacts will return to original state only after the reset time (“Delay-ON”) has elapsed.
Can be used in 3-wire and 4-wire network
User can adjust trip point (set point) and time delay settings.
The set point adjustment for over-voltage is in the range of 25%
As soon as the monitored signal moves outside of the set point limit, the time delay is activated, after which a trip will occur. The time delay prevents the relay from tripping for a predetermined period to prevent nuisance tripping.
The relay is automatically reset once the monitored voltage falls below the set point.
Adjustable off-delay: 0.1 …20sec
Adjustable reset-delay: 0.1…20sec
Adjustable over-voltage trigger range: 105% …130% (corresponding to 410V…510V AC)
LED indicators for relay activation during over-voltage condition
Relay output: Single change-over contact
Contact rating: 250V AC, 8A