(Sample Specification)
New Vacuum Replacement
Circuit Breakers
for
Westinghouse types
50-DH-150-1200 & 50-DH-150-2000
50-DH-250-1200 & 50-DH-250-2000
50-DHE-350-3000
75-DH-500-1200 & 75-DH-500-2000
150-DH-500-1200 & 150-DH-500-2000
150-DH-750-1200 & 150-DH-750-2000
50-DHP-350-1200 & 50-DHP-350-2000
75-DHP-500-1200 & 75-DHP-500-2000
150-DHP-500-1200 & 150-DHP-500-2000
150-DHP-750-1200 & 150-DHP-750-2000
150-DHP-750C-1200 & 150-DHP-750C-2000
150-DHP-1000-1200 & 150-DHP-1000-2000
1 General
This specification covers the design, testing and manufacturing requirements for new replacement medium voltage vacuum circuit breakers. The circuit breakers shall be a direct mechanical and electrical replacement for WESTINGHOUSE type DH AND DHP circuit breakers. The replacement vacuum circuit breakers shall be interchangeable between different cells of the same voltage, MVA and ampere class without cell modifications.
2 Scope of Work
Provide all project management, engineering, supervision, labor, material, tools, rental, test equipment and transportation as defined by this specification for a complete vacuum breaker replacement of the existing medium voltage switchgear circuit breakers listed in Section 3.0 “Equipment List”. The circuit breakers may be 4.76kV, 8.25kV or 15 kV class circuit breakers as designated.
3 Increased MVA Ratings
3.1 Switchgear line-ups designated for new replacement circuit breakers with increased MVA levels shall have the bracing verified to comply with the new maximum fault close and latch capabilities as well as the new breaker momentary ratings per ANSI C37.09.4.6.2.4 and ANSI C37.20.2.5.2.4.
3.2 The contractor shall perform a study to determine the current bracing capabilities and provide mathematical documentation to support his findings. The contractor shall state that the switchgear is sufficiently braced to handle the new ratings or supply the cost as a separate item to increase the bus bracing in all cubicles in the line-up to comply with the increased MVA ratings.
3.3 Following the study and/or the bracing modifications, the contractor shall affix a nameplate to the switchgear structure stating the new MVA rating, the contractor name and the certification date.
4 Cubicle Modifications
The new replacement circuit breakers shall be interchangeable with existing breaker of the same continuous current and MVA ratings without modifications to the existing cubicles or cell code plates unless specifically noted in these specifications.
Increased MVA ratings shall require a modification to the cubicle coding system to prevent the insertion of lower MVA rated circuit breakers or the existing circuit breakers into the cubicles intended for use with the new higher MVA class circuit breakers.
5 Equipment List
The vacuum circuit breakers shall be utilized to replace the following breakers currently in service at (Location or Substation):
5.1 Replacement circuit breakers for type DH air magnetic circuit breakers.
Qty / CAT. Type / kV / Amps / MVA / MOC / Number of MOC Tiers(1, 2, or 3)
50-DH-250-1200 / 5 / 1200 / 250 / Yes/No
50-DH-250-2000 / 5 / 2000 / 250 / Yes/No
50-DHE-350-3000 / 5 / 3000 / 3000 / Yes/No
75-DH-500-1200 / 7.5 / 1200 / 750 / Yes/No
75-DH-500-2000 / 7.5 / 2000 / 750 / Yes/No
150-DH-500-1200 / 15 / 1200 / 500 / Yes/No
150-DH-500-2000 / 15 / 2000 / 500 / Yes/No
150-DH-750-1200 / 15 / 1200 / 750 / Yes/No
150-DH-750-2000 / 15 / 2000 / 750 / Yes/No
150-DH-1000-1200 / 15 / 1200 / 1000 / Yes/No
150-DH-1000-2000 / 15 / 2000 / 1000 / Yes/No
5.2 Replacement circuit breakers for type DHP air magnetic circuit breakers.
Qty / CAT. Type / kV / Amps / MVA / MOC / Number of MOC Tiers(1, 2, or 3)
50-DHP-350-1200 / 5 / 1200 / 350 / Yes/No
50-DHP-350-2000 / 5 / 2000 / 350 / Yes/No
75-DHP-500-1200 / 7.5 / 1200 / 750 / Yes/No
75-DHP-500-2000 / 7.5 / 2000 / 750 / Yes/No
150-DHP-500-1200 / 15 / 1200 / 500 / Yes/No
150-DHP-500-2000 / 15 / 2000 / 500 / Yes/No
150-DHP-750-1200 / 15 / 1200 / 750 / Yes/No
150-DHP-750-2000 / 15 / 2000 / 750 / Yes/No
150-DHP-750C-1200 / 15 / 1200 / 1000 / Yes/No
150-DHP-750C-2000 / 15 / 2000 / 750 / Yes/No
150-DHP-1000-1200 / 15 / 1200 / 1000 / Yes/No
150-DHP-1000-2000 / 15 / 2000 / 1000 / Yes/No
6 Applicable Standards
All medium voltage replacement circuit breakers shall be designed, manufactured and tested in accordance with the applicable sections of:
ANSI C37.04 / ANSI C37.55ANSI C37.06 / ANSI C37.100
ANSI C37.09 / IEEE STD 4-1995
ANSI C37.20.2 / ANSI/NFPA 70 (NEC)
7 Materials
All materials shall be new and unused. No parts from the original circuit breaker shall be reconditioned and reused in the new replacement breaker.
7.1 Contractor/Vendor Qualifications
7.1.1 The supplier or manufacturer, hereafter designated as “contractor”, must meet the following qualifications to be considered for the award of the contract. The contractor shall have a minimum of ten years experience in a combination of performing vacuum conversions and/or the manufacture of vacuum replacement circuit breakers.
7.1.2 A reference list, preferably of utility and large industrial projects, shall be supplied with the bid for the circuit breakers.
7.1.3 Contractor shall supply evidence of ANSI/IEEE certification of the circuit breaker element and the completed assembly prior to delivery.
7.1.4 Contractor shall have local switchgear service engineers. The contractor shall have a minimum of 30 years experience in the maintenance of medium voltage switchgear. Provide address and telephone number of the service office nearest to the job site with the bid proposal.
7.1.5 All contractors are required to verify nameplate data, control wiring requirements and cell-to-breaker interface. If the contractor requires a site visit, contact the department issuing the request for bid to coordinate.
8 Vacuum Element Features
8.1 General
The retrofit or replacement breaker shall utilize one of the vacuum elements manufactured by Siemens Power Transmission and Distribution. Acceptable conversion units are types 3AF and 3AH. The breaker design shall use a common operator design across all ratings, e.g. a “breaker family”. The operator design shall include ratings of IEC and ANSI standards including ratings of 38kV/40kA and 15kV/63kA. In addition to the standard ANSI reclosing duties, multiple reclosing duties of O-3min-CO-3min-CO shall be available for all ratings and extended reclosing duty of O-0.3s-CO-15s-CO-15s-CO-15s shall be available for ratings up to 31.5kA.
8.2 Mechanical and Electrical Life
The breaker family shall include circuit breakers suitable for frequent operation with mechanical service life of up to 120,000 operations. The breaker element employed in any retrofit under these specifications shall have a mechanical design life of at least 10,000 mechanical operations and the vacuum interrupters with a life of at least 10,000 full load current switching operations and at least 20 full fault current switching operations.
The breaker shall be capable of up to 10,000 cycles or 10 years under normal operating conditions without re-lubrication and readjustment.
8.3 Element Frame
The vacuum element mechanism frame shall be welded and constructed of a minimum of 3/16 (7 GA.) material to ensure strength, rigidity and dimensional stability over the life of the breaker.
8.4 Common Pole Shaft
The circuit breaker mechanism shall open and close all three phases and any auxiliary devices via a common operating shaft to ensure consistent and simultaneous operation of the main contacts. The main drive shaft shall be connected to the individual vacuum interrupters via insulated drive links. The drive links shall employ contact pressure springs that transfer the closing motion from the pole shaft to the contacts through roller bearings to ensure smooth operation. It shall be possible to move the pole shaft into the closed and latched position employing a closing bar (i.e. slow close the mechanism) to ensure smooth operation without evidence of binding or to check and adjust the synchronization of the contacts.
8.5 Insulated drive links
The mechanism drive shaft shall be connected to each moving contact via an insulated drive link. The insulated link material shall be non-hydroscopic and meet the flame-retardant requirements as set forth in ANSI C37.20.2. The drive links shall be easily removable with single pins at each end and spring retaining clips. Due to the extremely long life specified, it shall be possible to adjust the length of the drive links for the purposes of adjusting or balancing vacuum interrupter stroke over the life of the breaker or should vacuum interrupter replacement be necessary.
8.6 Shock Absorber System
The mechanism shall contain a shock absorber system to dampen the opening force of the circuit breaker. The shock absorber shall have sufficient resilience to prevent contact bounce that could cause a restrike of the main contacts during the opening of the circuit breaker. The element shall have a sealed replaceable shock absorber and shall be capable of being adjusted if replaced or during initial mechanism assembly. The shock absorber shall have a design life of 30,000 breaker opening and closing cycles without the need for repair, replacement or adjustment.
8.7 Manual and Electrical Tripping and Closing
The mechanism shall have front accessible manual close and trip operators that are independent of the electrical trip and close coils. The trip and close solenoids shall be capable of hand operation with the front cover removed to check for binding or unusual force. The mechanism shall be able to accommodate one closing solenoid and up to three tripping releases -- two shunt releases and either an undervoltage release or a low energy (0.1Ws) current transformer operated release.
8.8 Operations Counter
Each breaker mechanism shall have a five (5) digit non-resetting mechanical operations counter connected to the operating shaft.
8.9 Spring Charged Indicator
Each operating mechanism shall be equipped with a visible indicator to show the state of the stored energy mechanism. The indicator shall display the word ‘charged’ in black letters on a yellow background when the spring is fully charged and ‘discharged’ in black letters on a white background when the springs are discharged. Additionally, the spring charged state shall be available through both an ‘a’ and a ‘b’ contact which are independent of any other circuits.
8.10 Auxiliary Devices
The breaker shall have a low inertia, rotary operated auxiliary switch connected to the main pole shaft assembly. The auxiliary switches shall have a continuous current capability of 10A, making current of 50A, and a breaking capacity at 220 VDC of 2A (T=2ms). Wiring shall be at least AWG 16-gauge class C halogen free and flame retardant insulation. Terminations shall be either self-locking push on connectors or ring tongue. If ring tongue terminations are used a positive method such as lock washers shall be employed to ensure the ring tongue connections remains tight.
8.11 Corona Suppression
The element, to the greatest degree possible, shall minimize the possibility of corona generation. Sharp edges, points and punched parts with burrs and points shall be avoided. Where sharp edges or points cannot be eliminated, corona shields with rounded edges shall be incorporated into the design to distribute and even out the electric field.
8.12 Vacuum Bottle Assembly
The vacuum bottle assembly shall be constructed from virgin materials and shall be a Siemens Product or engineer approved equal. The edges of the ceramic components shall be “metalized” and fired prior to assembly. The components shall be inspected and assembled in a class 1000 clean room prior to sealing the components. The components shall be inserted into a vacuum heat chamber and sealed under vacuum. A stainless steel corrugated bellows shall achieve isolation of the ambient air and the vacuum. The vacuum interrupter shall have a visual method of identifying contact wear (contact erosion) without the use of gauges or other devices.
8.13 Vacuum Interrupter Contacts
The contacts shall principally be composed of unalloyed chromium-copper contact material. The contacts shall be machined to form spiral petal contacts to assist in the swirling of the arc during interruption. Contacts up to 50kA interrupting shall use a radial magnetic design, 50kA and higher interrupting shall employ axial magnetic contacts.
Following assembly onto the breaker element, the interrupters shall be put through a conditioning process to work harden the contacts and as assurance of bellows integrity in actual operation. Contact erosion indicators shall not be affixed until after contact conditioning. The conditioning process shall nominally consist of 300 cycles but may be shortened if numerically controlled test equipment indicates that full conditioning has been achieved.
8.14 Insulated Pole Assemblies
Pole assemblies shall be insulated from ground with non-hydroscopic insulating standoffs. Construction of the pole assemblies shall be such that it shall be possible to access all sides of the vacuum interrupters for cleaning and inspection. It shall be possible to replace individual vacuum interrupters without the need of replacing an entire pole assembly.
8.15 Current Transfer System
The current transfer from the vacuum interrupter moving stem to the breaker terminals assemblies shall be via a non-sliding current transfer system consisting of a copper stem clamp and silver plated copper leaf conductors. It shall be possible to verify the adequacy of the moving stem connection and tighten or replace the assembly if necessary. All connections in the primary current path shall be silver plated.
8.16 Trip Free Operation
The new circuit breaker operation mechanism shall be a “true Trip-Free” design. When the trip function is mechanically engaged and held and the close function is initiated either electrically or mechanically, the contacts shall not close. The contacts shall be restricted to 10% of the total travel. Execution of the trip–free function shall not degrade breaker life or cause the closing springs to impact upon any components other than snubbers.
8.17 Mechanical Status Indicator
Each new vacuum replacement breaker shall have a mechanical status indicator with the word "CLOSED" on a red background when the circuit breakers are closed and the word "OPEN" on a green background when the circuit breakers are open.
9 Replacement Breaker Assembly
9.1 Frame
The frames shall be constructed from steel. Bolted construction is preferred over a welded configuration. All steel components used in the frame shall be painted with powder coat paint, ANSI 61 light gray finish, or plated with Type II yellow zinc dichromate.
9.2 Wheels and Casters for Transport
Replacement circuit breakers shall be supplied with a functional replacement of the transport systems of the original design.