GE Multilin 850

CHAPTER 4: SETPOINTS SYSTEM
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL 4–81
Recloser curve selection is special in that recloser curves can be shaped into a composite
curve with a minimum response time and a fixed time above a specified Pickup multiple.
There are 41 recloser curve types supported. These definite operating times are useful to
coordinate operating times, typically at higher currents and where upstream and
downstream protective devices have different operating characteristics. The recloser
curve configuration window shown below appears when the Initialize From setting is set to
“Recloser Curve”.
Figure 4-19: Recloser Curve Initialization
MULTIPLIER: Scales (multiplies) the curve operating times.
Adder: Adds the time specified in this field (in ms) to each curve operating time value.
Minimum Response Time (MRT): If enabled, the MRT setting defines the shortest operating
time even if the curve suggests a shorter time at higher current multiples. A composite
operating characteristic is effectively defined. For current multiples lower than the
intersection point, the curve dictates the operating time; otherwise, the MRT does. An
information message appears when attempting to apply an MRT shorter than the
minimum curve time.
High Current Time: Allows the user to set a pickup multiple from which point onwards the
operating time is fixed. This is normally only required at higher current levels. The HCT
Ratio defines the high current pickup multiple; the HCT defines the operating time.
FAST PATH:
The multiplier and adder settings only affect the curve portion of the characteristic and not
the MRT and HCT settings. The HCT settings override the MRT settings for multiples of
Pickup greater than the HCT ratio.
FAST PATH:
The “Total Multiplier” used for calculation is equal to the product of the multiplier in the TOC
element and the multiplier in the recloser curve.
EXAMPLE
A composite curve can be created from the GE_111 standard with MRT = 200 ms and HCT
initially disabled and then enabled at eight (8) times Pickup with an operating time of 30
ms. At approximately four (4) times Pickup, the curve operating time is equal to the MRT
and from then onwards the operating time remains at 200 ms (see below).