ABB 615 Series ANSI, Техническое руководство, Страница: 234 / 713

1MAC050144-MB C
Section 4
Protection functions
615 series ANSI 227
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 IED 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.
4.2.1.5 Timer characteristics
The operating curve types supported by 59 are:
Table 222: Timer characteristics supported by IDMT operate curve types
4.2.1.6 Application
Overvoltage in a network occurs either due to the transient surges on the network or due
to prolonged power frequency overvoltages. Surge arresters are used to protect the
network against the transient overvoltages, but the IED protection function is used to
protect against power frequency overvoltages.
The power frequency overvoltage may occur in the network due to the contingencies such
as:
• The defective operation of the automatic voltage regulator when the generator is in
isolated operation.
• Operation under manual control with the voltage regulator out of service. A sudden
variation of load, in particular the reactive power component, gives rise to a
substantial change in voltage because of the inherent large voltage regulation of a
typical alternator.
• Sudden loss of load due to the tripping of outgoing feeders, leaving the generator
isolated or feeding a very small load. This causes a sudden rise in the terminal voltage
due to the trapped field flux and overspeed.
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
(17) Inv. Curve A
(18) Inv. Curve B
(19) Inv. Curve C
(20) Programmable