S3 - Distribution Equipment Flashcards
The most common protective devices on the distribution system
Expulsion Fuses
Used to protect overhead and underground primary taps, distribution transformers, and capacitor banks.
Fuses
EPB uses this type fuse mounting
XS Fuse Mounting
The most common type of expulsion fuses.
Type “K” for Kwik and type “T” for Tardy
EPB’s mostly used type fuse links
T
This depends on the downstream peak load current, available fault current and upstream protection devices.
Fuse Link
This is sized to coordinate with the upstream devices, meaning it will interrupt the load for a fault behind it without any other upstream device operating.
The Fuse
Used in most single phase pad mounted transformers and are also used in some of the large three phase pad mounted transformers at Hamilton Place Mall.
Bayonet Fuses
The are two types of bayonet cartridges are:
Load Sensing & Fault Sensing
A self-controlled device for automatically interrupting and reclosing an alternating-current circuit, with a predetermined sequence of opening and reclosing followed by resetting, hold closed, or lockout
Recloser
Interrupting Mediums
Oil, Air, SF6, Vacuum
The primary purpose of a reclosing device
To allow temporary faults an opportunity to clear themselves
Uses springs and hydraulic systems for timing and actuation for reclosing
Hydraulic Recloser
What happens if a temporary fault is located behind the recloser in ideal conditions?
Ideally one reclosing cycle permits the temporary fault to clear and service is restored to all the customers downstream
What happens if the temporary fault is located behind a fuse downstream from a recloser in ideal conditions?
The fuse may blow isolating the fault from the mainline and interrupting service for customers downstream from the fuse, or the fuse may remain in tact long enough for the recloser to operate once on the fast curve. If the fault has cleared, service may be restored to all customers
When reclosers are in service are bypasses open or closed?
Open, when closed the recloser has been removed from the circuit
A type of reclosing device that interrupts the fault similar to a recloser, but instead of closing back into the fault to determine if the fault is still affecting the system this device pulse closes to intelligently test for fault current before closing.
Three Phase Pulse Circuit Recloser or Three Phase PulseCloser
Are self-contained, circuit opening devices used in conjunction with a recloser, to automatically isolate faulted sections of a feeder
Sectionalizers
This device senses current flow above a preset level, and when the source side protective device opens to de-energize the circuit, the device counts the overcurrent interruption.
Sectionalizer
This device is set to count a certain number of interruptions and when it reaches the full count it will open, but this is device is not designed to interrupt fault current and can break load.
Sectionalizer
This device is used to add a level of protection where other devices cannot be coordinated with the upstream or downstream devices.
Sectionalizer
Devices used to control and route the flow of power through electrical lines
Switches
This device is not a protective device that will automatically open for system faults
Switches
Devices that can be used to drop load and are equipped with some method of extinguishing the arc when load is being dropped.
Load Break Switches
This must be used when switching between two feeders off of different sources
Load Break Switch
