Method Of Operation - Siemens SIPROTEC 7SA522 Manual

2 Functions

2.13.1 Method of Operation

Figure 2-98 Timing diagram of a double-shot reclosure with action time (2nd reclosure successful)
Selectivity before
Reclosure
228
Reclosure is performed by an automatic reclosure function (AR). An example of the
normal time sequence of a double reclosure is shown in the following Figure.
The integrated automatic reclosure circuit allows up to 8 reclosure attempts. The first
four interrupt cycles may operate with different parameters (action and dead times,
single/three-pole). The parameters of the fourth cycle also apply for the fifth cycle and
onwards.
In order for the automatic reclosure to be successful, all faults on the entire overhead
line must be cleared at all line ends simultaneously — as fast as possible. In the dis-
tance protection, for example, the overreaching zone Z1B may be released before the
first reclosure. This implies that faults up to the zone reach limit of Z1B are tripped
without delay for the first cycle (Figure 2-99). A limited unselectivity in favour of fast
simultaneous tripping is accepted here because a reclosure will be performed in any
case. The normal stages of the distance protection (Z1, Z2, etc.) and the normal
grading of the other short-circuit functions are independent of the automatic reclosure
function.
7SA522 Manual
C53000-G1176-C155-3