ABB RER620, Техническое руководство

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Section 4
Protection functions
RER620 203
Technical Manual
Blocking logic
There are three operation modes in the blocking functionality. The operation modes are
controlled by the
BLOCK
input and the global setting Configuration > System > Blocking
mode which selects the blocking mode. The
BLOCK
input can be controlled by a binary
input, a horizontal communication input or an internal signal of the relay program. The
influence of the
BLOCK
input signal activation is preselected with the global Blocking
mode setting.
The Blocking mode setting has three blocking methods. In the “Freeze timers” mode, the
operate timer is frozen to the prevailing value. In the “Block all” mode, the whole function
is blocked and the timers are reset. In the “Block TRIP output” mode, the function operates
normally but the
TRIP
output is not activated.
4.3.2.5 Timer characteristics
The operating curve types supported by 27 are:
Table 210: Supported IDMT operate curve types
4.3.2.6 Application
27 is applied to power system elements, such as generators, transformers, motors and
power lines, to detect low voltage conditions. Low voltage conditions are caused by
abnormal operation or a fault in the power system. 27 can be used in combination with
overcurrent protections. Other applications are the detection of a no-voltage condition, for
example before the energization of a high voltage line, or an automatic breaker trip in case
of a blackout. 27 is also used to initiate voltage correction measures, such as insertion of
shunt capacitor banks, to compensate for a reactive load and thereby to increase the
voltage.
27 can be used to disconnect from the network devices, such as electric motors, which are
damaged when subjected to service under low voltage conditions. 27 deals with low
voltage conditions at power system frequency. Low voltage conditions can be caused by:
• Malfunctioning of a voltage regulator or incorrect settings under manual control
(symmetrical voltage decrease)
• Overload (symmetrical voltage decrease)
• Short circuits, often as phase-to-ground faults (unsymmetrical voltage increase).
The “Freeze timers” mode of blocking has no effect during the “Inverse
reset” mode.
Operating curve type
(5) ANSI Def. Time
(15) IEC Def. Time
(21) Inv. Curve A
(22) Inv. Curve B
(23) Programmable