Description Of Functionality - Siemens 7SR224 Argus Manual

Description of Functionality

With reference to figure 8: 'Function Diagram'.
25 Synchronising
Synchronising is used with three pole Manual Closing and
Autoreclose operations to ensure that voltages are within
safe limits before allowing the close operation to proceed.
The 7SR224 provides settings for voltages, phase and
frequency difference for Check Synchronising as well as
System Synchronising and Close on Zero phase difference for
automatic selection following detection of a split system.
Automatic Synchronising bypass is also available to allow
closure to energise a dead feeder or busbar.
27/59 Under/over Voltage
4 elements which can be set independently as Under or
overvoltage. Each element has settings for pickup level and
Definite Time Lag (DTL) delays, operates if voltage 'exceeds'
setting for duration of delay, Typically applied in load
shedding schemes.
37 Undercurrent
2 element with settings for pickup level and Definite Time
Lag (DTL) delays. Each operates if current falls below its
setting for duration of its delay.
46BC Broken Conductor
Each element has settings for pickup level and DTL delay.
With the circuit breaker closed, if the NPS / PPS current ratio
is above setting this could be due to a broken conductor.
46NPS Negative Phase Sequence Overcurrent
Two elements, one DTL and one IDMT, with user settings for
pickup levels and delays. NPS Current elements can be used
to detect unbalances on the system. The negative sequence
phase component of current is derived from the three phase
currents. It is a measure of the quantity of unbalanced
current on the system.
47NPS Negative Phase Sequence OverVoltage
Two DTL elements with independent user settings for NPS
overvoltage pickup level and delays. NPS Voltage elements
can be used to detect unbalances on the system. The
negative sequence phase component of voltage is derived
from the three phase voltages. It is a measure of the
quantity of unbalanced voltage on the system.
49 Thermal Overload
The thermal algorithm calculates the thermal state of each
pole from the measured currents and can be applied to lines,
cables and transformers; operates if the user set thermal
overload is exceeded. Capacity Alarm operates if a user set
percentage of overload is reached.
Siemens Protection Devices Limited
50BF Circuit Breaker Fail
The circuit breaker fail function may be triggered from an
internal trip signal or from a binary input. All measured
currents can be monitored following a trip signal and an
output is issued if any current is still detected after a
specified time interval. This can be used to re-trip the CB or
to back-trip an upstream CB. A second back-trip time delay is
provided to enable another stage to be utilized if required.
59N Neutral Overvoltage
Two elements, one DTL and one IDMTL, have user settings
for pickup level and delays. These will operate if the Neutral
voltage exceeds the setting for duration of delay. Neutral
overvoltage can be used to detect earth faults in high
impedance earthed or isolated systems.
67/50 Phase Fault Elements
Provide Directional Instantaneous or Definite Time (DTL)
Overcurrent protection, with independent settings for pickup
current and time-delay.
Four elements are provided.
Elements can be Inrush-inhibited
67/51 Phase Fault Elements
Provide Directional - Inverse Definite Time Overcurrent
protection, TCC/DTL with independent settings for pickup
current, TCC and minimum/follower time-delay.
Four elements are provided.
User can select the TCC from standard IEC/ANSI or Legacy
Characteristics e.g. 101 (A) etc. Reset TCC can be user set to
either DTL or shaped, to integrate grading with
electromechanical or other protection devices.
Earth Fault/Sensitive Earth Fault
The Earth Fault current is measured directly via a dedicated
current analogue input. This input is used for both Earth
Fault and Sensitive Earth Fault elements.
67/50G Earth Fault
Provide Directional Instantaneous or Definite Time (DTL)
earth fault protection, with independent settings for pickup
current and time-delay.
Four elements are provided.
Elements can be Inrush-inhibited.
67/51G Earth Fault
Provide Directional - Inverse Definite Time earth fault
protection, TCC/DTL with independent settings for pickup
current, TCC and minimum/follower time-delay.
Four elements are provided.
User can select the TCC from standard IEC/ANSI or Legacy
Characteristics e.g. 101 (A) etc. Reset TCC can be user set to
either DTL or shaped, to integrate grading with
electromechanical or other protection devices.
67/50SEF Sensitive Earth Fault
Provide Directional Instantaneous or Definite Time (DTL)
earth fault protection, with independent settings for pickup
current and time-delay.
Four elements are provided.
Elements can be Inrush-inhibited
4