TCP high-voltage SF6 power circuit breaker

06/01/2005 - Volume II - Issue II

Maintenance matters - hints for maintenance Siemens TCP high-voltage SF6 power circuit breaker

 

Thorough, periodic inspection is important to satisfactory operation. Inspection and maintenance frequency depends on installation, site, weather, and atmospheric conditions, experience or operating personnel, and special operation requirements. Because of this, a well-planned and effective maintenance program depends largely on experience and practice.

 

Periodic inspections should be made at monthly and semi-annual intervals to ensure continued satisfactory performance. After three and six years of service, it is recommended that you consider a general external inspection.

 

Depending on the results of the three and six year inspections and the accumulated amount of interrupting duty, whichever comes first:

  • 20 times the interrupting rate (i.e. 20 full-rated faults, 40 half-rated faults)
  • 3,000 mechanical operations
  • 12 years of service.

Siemens recommends a Major Inspection which requires the removal of gas from the breaker to determine the condition of the interrupters, contacts, and other internal components.

General hints

Handling or moving TCP circuit breakers

 

Always use steel cable slings or chains of the proper length in lifting or moving TCP breakers. In addition to the information in the Instruction Book, there are two decals on each breaker showing how to lift and the proper sling length.

 

Do not use nylon slings which can have uncontrolled stretch and result in instability when lifting the breaker.

 

Rusting CT covers

 

On some TCP breakers built before June of 1993, we have received reports of rusting on the CT can coverplate. This situation appears to be most significant in high humidity salt contaminated areas such as near seacoasts. The coverplate is a split ring zinc dichromate coated steel plate attached and sealed to the porcelain flange and the aluminum CT spinning with the screw and RTV. This rust can be repaired in the following ways:

  1. In cases of light rust, simply wire brush and touch up with primer paint.
  2. In more severe cases, again wire brush to remove the loose rust and then coat with Loctite Extend (part number W963503). After this dries it can be painted with touch up paint. Note: The touch up paint and the Loctite Extend may not stick to the RTV, but should help prevent rusting under the RTV.
  3. At the time of major maintenance on the breaker, if desired, the steel plates can be changed out to aluminum. The aluminum split rings may be ordered using the part numbers as follows:

Voltage                 Interrupter-side                   Bushing-side

121/145                72-180-263-001                 72-180-261-001

169/242                72-180-806-001                 72-180-807-001

 

Transition housing cover leaks

 

Some of our customers have reported water leaking into the transition housing at the cover. Investigation has revealed that the water is leaking past the housing bolts.

 

On existing breakers, the situation is easily corrected by adding a second larger neoprene washer part number 72-182-048-001 under the existing washer. This covers the slot that was open to leakage. The use of RTV (silicone rubber) along with the top edge is another way to affect a seal. The drawback to this method is that the seal gasket tends to be damaged each time the cover is removed.

 

The situation has been addressed on new breakers by removing the slots and relocating the bolt holes. New revised covers, part number 72-180-544-501, and sealing, part number W37000504 (quantity 8), may be ordered free of charge. When installing covers on TCP breakers, start the middle cover bolts first and then either the top row of bolts or the bottom row of bolts.

 

After any leaking around the cover is corrected, remove any loose rust from the housing by use of a wire brush or a Scotchbrite pad. (Caution: Use care to protect the stainless steel operating shaft from loose abrasive material of any type.) Paint the rusty area witha  rust conversion coating material such as "Extend." Additional painting is not necessary.

 

Hydraulic system leaks

 

Pressure relief valve

 

On the TCP breakers built before January 1992, a "dart" type relief valve was used. This valve has a dart and anvil seat that was occasionally sensitive to foreign material. The valve could begin to leak high pressure to low pressure and would not reseal and as a result the pump motor may run continuously, causing property damage to the TCP breaker. This relief action is most common in locations where there are large changes in temperature night to day. This valve was changed in January 1992 to W43840801. This valve is of the direct acting ball type and will fit directly into the cavity of the earlier valve. The current valve has solved  the problem of leaking relief valves and can be obtained from SE&A at no charge. The new valve uses crushable copper washers as a means of sealing to atmosphere. These washers should be replaced if the cover is removed or the valve adjusted. Use care on torquing the cover and locknut to 13ft. lbs.

 

Pressure switches

 

Hydraulic leaks have been reported at the adapter nipple used to connect the pressure switch to the manifold. This can normally be corrected by disassmbly and retightening with new pipe dope (recommend Loctite 567-65 sealant part number W946027) which is Teflon filled. Let the pipe dope harden for 16 hours before reinstalling.

 

New breakers no longer use this pipe nipple but will hvae a ring seal only. A kit which will convert the pipe thread seal stem to the ring system may be ordered at customer's expense (part number 72-182-158-801, 802, 803) for 1,2, and 3 switches respectively if desired.

 

Pressure gauge fitting

 

Some hydraulic leaks may develop at the back of the pressure gauge. There is a "seal" ring that must be centered before tightening this fitting. Due to its location, it is difficult to center this ring easily. A new "usit" ring is now available at no charge. It is part number W370-006-13 and has proven very easy to assemble and effective in solving leaks.

 

Breaker upgrades

 

If you have a need to either increase the performance of your TCP or to bring it up to current design configurations:

  • Breakers can be upgraded to 50kA with the addition of line to ground capacitors and some interrupter parts changes. A support structure that mounts to the existing breaker frame is available.

  • Breaker uprate kits to 63kA are available for 169kV and 242kV with additional charges. Upgrading to these highger ratings is suitable for on-site conversions.

  • Heater kits are available for operation at ambient temperatures to -50 degrees Celsius.

  • Breakers can be uprated to meet seismic zone 3 or 4.

  • Upgrade SF6 manifold with sampling valve.


* THESE INSTRUCTIONS DO NOT PURPORT TO COVER ALL DETAILS OR VARIATIONS IN EQUIPMENT, NOR TO PROVIDE FOR EVERY POSSIBLE CONTINGENCY TO BE MET IN CONNECTION WITH INSTALLATION, OPERATION OR MAINTENANCE. SHOULD FURTHER INFORMATION BE DESIRED OR SHOULD PARTICULAR PROBLEMS ARISE WHICH ARE NOT COVERED SUFFICIENTLY FOR YOUR PURPOSES, THE MATTER SHOULD BE REFERRED TO THE LOCAL SIEMENS SALES OFFICE. THE CONTENTS OF THESE INSTRUCTIONS SHALL NOT BECOME PART OF OR MODIFY ANY PRIOR OR EXISTING AGREEMENT, COMMITMENT OR RELATIONSHIP. THE SALES CONTRACT IF ANY CONTAINS THE ENTIRE OBLIGATION OF SIEMENS. THE WARRANTY CONTAINED IN ANY CONTRACT BETWEEN THE PARTIES IS THE SOLE WARRANTY OF SIEMENS. ANY STATEMENTS CONTAINED HEREIN DO NOT CREATE NEW WARRANTIES OR MODIFY THE EXISTING WARRANTY.