Accuracy Of Measurement; Checking The Thermal Characteristic - Siemens 7SG23 MSCDN – MP2A Manual

characteristic with the parameters A =1second, P = 2 and Q = 1 may be used if a full thermal curve is required.
Pickup and Time constant should be as applied to relay.
Ensure that the resistor thermal elements are disabled at this stage to avoid confusing results.
Gn R1 49 Thermal Overload
Selects whether the thermal overload protection element is
enabled for Resistor R1
Gn R2 49 Thermal Overload
Selects whether the thermal overload protection element is
enabled for Resistor R2
Ensure that the resistor open circuit elements are disabled at this stage to avoid confusing results.
Gn 50 OC
Selects whether the DTL Resistor Open Circuit Overcurrent
element is enabled

8.1 Accuracy of Measurement

Inject all of the current inputs with nominal current in turn, and record the Relay Currents measured by the
relays in the table below.
If the relay measurement is within tolerance proceed to 9.2 below. If any of the measurements are outside the
stated tolerance (±5%) the relay must be sent back to the Quality Assurance Department for investigation.

8.2 Checking the thermal characteristic

Enable the thermal elements.
Gn R1 49 Thermal Overload
Selects whether the thermal overload protection element
is enabled for Resistor R1
Gn R2 49 Thermal Overload
Selects whether the thermal overload protection element
is enabled for Resistor R2
When testing the thermal characteristic, the status each thermal element can be displayed on the LCD by
changing to the INSTRUMENTS mode and scrolling down to either [R1 METERS] or to [R2 METERS] as
required. The Instruments to view to help check the relay thermal characteristics are
INSTRUMENT
[ R1 METERS ]
--> press down <--
R1 Primary Currents
0.0 0.0 0.0 kA
R1 Nom Currents
0.00 0.00 0.00 xIn
R1 Thermal Status
0.0 0.0 0.0 %
[ R2 METERS ]
--> press down <--
R2 Primary Currents
0.0 0.0 0.0 kA
R2 Nom Currents
0.00 0.00 0.00 xIn
R2 Thermal Status
0.0 0.0 0.0 %
The thermal status meters show the current thermal state of the elements. When applying secondary injection
current these values will change to show how the resistor model is warming up. Sufficient time must be
allowed between tests to allow the thermal model to reset otherwise operate times may be misleading. To
©2010 Siemens Protection Devices Limited
Disabled, Enabled
Disabled, Enabled
Disabled, Enabled
RESISTOR
R1
R2
Disabled, Enabled
Disabled, Enabled
Start of resistor 1 meters
Resistor 1 primary currents (requires CT ratios to be entered correctly)
Resistor 1 secondary nominal currents
Resistor 1 thermal status, 100% = Fully operated, 0-99% = thermal state of
resistors
Start of resistor 2 meters
Resistor 2 primary currents (requires CT ratios to be entered correctly)
Resistor 2 secondary nominal currents
Resistor 2 thermal status, 100% = Fully operated, 0-99% = thermal state of
resistors
MSCDN – MP2A Commissioning
Disabled
Disabled
Disabled
A B
Enabled
Enabled
DESCRIPTION
Chapter 7 Page 6 of 9
C