A properly rated sectionalizer must be selected for each installation with consideration to the following:
- System voltage
- Continuous current
- Actuating current
- Number of counts for operation
- Upstream and downstream protective devices
The sectionalizer must have a voltage rating equal to or greater than the system voltage.
Minimum Actuating Current:
The minimum actuating current of sectionalizers should be 80% of the phase minimum trip of the source side single phase automatic circuit recloser.
Where three phase reclosers or circuit breakers are used, a user may want to co-ordinate sectionalize actuating current with the ground trip rating.
Where hydraulic reclosers are used, this is easily accomplished by matching the sectionalizer and the recloser’s continuous current ratings.
The sectionalizer’s minimum actuating current is 160% of its continuous current rating and the hydraulic reclosers’ phase pick-up is 200% of its continuous current rating (160/200=.80). (Table A).
Number of Counts:
The sectionalizer should be set to operate in at least one less count than the backup recloser.
Example: a 4-shot recloser would require a maximum of a 3-count sectionalizer downstream (Figure 2, line A).
In case of a 2-fast/2-slow reclose setting, a 2-count sectionalizer may be used to reduce the number of recloser operations (Figure 2, line B).
Where sectionalizers are used in series, the downstream sectionalizer should have one less count than the upstream sectionalizer (Figure 3).
Upstream & Downstream Devices:
The reclose time (dead time between shots) of the recloser must be shorter than the sectionalizer reset time. The sectionalizer reset time is the time that the memory is functional and retains prior counts.
The CRS reset time is two minutes for a current pulse equal to 1.3 times the actuating current (recloser’s minimum trip point).
Single-phase sectionalizers should be used with single-phase reclosers to avoid single-phasing of three-phase circuits. However, some utilities may permit single-phasing. In such cases, a single-phase sectionalizer may be used with a three-phase recloser.
If a fuse is downstream from a sectionalizer, the fuse must be coordinated with the recloser so the fuse will operate in at least one less count than the sectionalizer.
The sectionalizer can be used between two reclosers as long as there is at least 300mA of load current between the sectionalizer and the downstream recloser.
Immunity to lightning surge current:
Over-voltage protection is the user’s responsibility based on the user’s over-voltage protection practices. Chance Resettable Electronic Sectionalizers were tested to withstand 65kA lightning surge current as prescribed in ANSI/IEEE C37.63 and IEEE C6211 standards for surge arresters, making it immune to lightning surges up to 65kA.
|Recloser||Typical Sectionalizer Ratings|
|Minimum Trip, Amps||Minimum Actuating Current, Amps ± 10%||Continuous Current, Amps|
Table A. Recloser/sectionalizer coordination.