Description and Application

CP medium voltage switchgear is an integrated assembly of drawout vacuum circuit breakers, bus, and control devices coordinated electrically and mechanically for medium voltage circuit protection. The Metal-Clad integrity provides maximum circuit separation and safety. Included are isolated grounded metal components, complete insulation of all conductors insuring that the opening of a door will expose no live parts. It is typically used on circuits involving feeder circuits, transmission lines, distribution lines and motors.

Using CP to supply your switchgear needs establishes one source of responsibility for the equipment and assures high standards in quality, coordination, reliability, safety, and service.

CP medium voltage switchgear is available in voltage ratings of 2.4 kV through 15kV and in normal interrupting capacities of 250MVA (29kA), 350MVA (41kA), 500MVA (18kA and 33kA), 750MVA (28kA), 1000MVA (37kA), and 1500MVA (63 kA), and for indoor or outdoor applications.

** Please note that the latest standards from ANSI no longer consider "MVA" as a rating factor and further consider the range factor equal to 1.0. Now breakers are "sized" by their short circuit rating. At the end of this literature section you will find TABLE 1 as published from the latest version of ANSI C37.09 Medium Voltage Metal-Clad Circuit Breakers.

Metal-Clad Switchgear Definition

Metal-Clad Switchgear is an assembly of units characterized by the following features:

The main interrupting device is removable and arranged with a mechanism for moving it physically between connected and disconnected positions. It is equipped with self-aligning and self-coupling primary and secondary disconnecting devices.

The interrupting devices, buses, voltage transformers, and control power transformers, are completely enclosed by grounded metal barriers, which have no intentional openings between compartments. A metal barrier in front of the interrupting device ensures that when, in the connecting position, no live parts are exposed by the opening of an enclosure door.

All live parts are enclosed within grounded metal compartments.

Automatic grounded metal shutters cover primary circuit elements when the removable element is in the disconnected, test, or removed position.

Primary bus conductors and connections are covered with track-resistant insulating material throughout.

Mechanical interlocks are provided to maintain a proper and safe operating sequence and to ensure matching ampacities between circuit breaker and cell.

Grounded metal barriers isolate and ground instruments, meters, relays, secondary control devices, and their wiring from all primary circuit elements. If a short circuit or fault occurs, all damage is contained within the metal-clad enclosure.

Applicable Industry Standards

ANSI American National Standards Standard Institute

C37.010 Application Guide for AC High Voltage Circuit Breakers Rated on A Symmetrical Current Basis

C37.100 Definitions for Power Switchgear

C37.04 Rating Structure for AC High Voltage Circuit Breakers

C37.06 Preferred ratings for AC High Voltage

C37.07 Factors for reclosing service

C37.09 Test procedure for AC High Voltage Circuit Breaker

C37.11 Power Circuit Breaker Control

C37.20.2 Metal-Clad and Station-Cubicle Switchgear

1 C37.21 Application Guide for Metal-Enclosed Switchgear

1 C37.55 Conformance Testing of Metal-Clad Switchgear

C37.24 Guide for evaluating the effect of solar radiation

NEMA National Electrical Manufacturers Association

SG-4 Power Circuit Breakers

SG-5 Power Switchgear Assemblies

*** UL Listed on Specific Designs ***

Design/Proof Tests

CP metal-clad switchgear meets applicable ANSI, IEEE, and NEMA standards. The design criteria dictated that all tests demonstrate performance equal to or above the requirements of the standards. The ANSI test series is basic test criteria and includes interruption, BIL, dielectric, continuous current, mechanical life, and thermal and environmental conditions.

Productions Test - Circuit Breaker

Each breaker drawout unit is checked for alignment with a master cell fixture that verifies all interfaces and interchangeability. All circuit breakers are operated over the range of minimum to maximum control voltage. Interrupter contact gap is factory set. One-minute dielectric test is performed on each breaker, per ANSI standards. Final inspection and quality check.

Housing

An actual circuit breaker of each current size is inserted into each breaker cell to ensure alignment. One-minute dielectric test per ANSI standards is applied to both primary and secondary circuits. Operation of wiring, relays, and other devices is verified by test. Final inspection and quality check.

Switchgear Features

1. Vacuum Interrupter – All circuit breakers are low maintenance, high reliability vacuum interrupters. Cutler Hammer or General Electric designs are standard. Siemens or ABB designs are optional.

2. Breaker Rails – The breaker and auxiliaries can be withdrawn on rails for inspection and maintenance.

3. Front Breaker Mechanism – The stored energy mechanism is on the front of the breaker so the inspection or maintenance can be done with the breaker on its rails (Cutler Hammer design).

4. Horizontal Drawout Circuit Breaker – A horizontal drawout design that provides connect, test, and disconnect positions. Direct roll-in design is available for General Electric breakers. A ramp or lift device is required for Cutler Hammer breakers.

5. Automatic Shutters – These grounded steel shutters operate automatically when the circuit breaker is withdrawn in order to protect workmen from accidental contact with the stationary primary contacts.

6. Main Bus System – The main bus has fluidized-bed, track-resistant epoxy insulation with silver-plated joints and constant pressure washers. Vinyl boots are used on all bus joints.

7. Current Transformers – There is space for up to four standard accuracy current transformers per phase, which are easily accessible from the front. Two high accuracy current transformers per phase can be used instead of four standard accuracy current transformers.

8. Primary and Secondary Contacts – All moving breaker contacts are self-aligning, self-coupling, have positive action, and are silver-plated.

9. Metal Compartment Barriers – All compartments are enclosed by grounded metal barriers.

10. Breaker Wheels – Breakers can be rolled on floor surfaces when removed from the structure.

11. Auxiliary Compartment Shutter – This shutter operates automatically when the auxiliary drawer is withdrawn to protect workmen from accidental
contact with the stationary primary contacts.

Click here to view the 15kV Metal-Clad Switchgear Guide Specifications.

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