High Voltage Apparatus Bushing Creepage

The minimum bushing creepage required for the areas with different contamination levels is well defined in IEEE Std C57.19.100.

The areas with contamination levels light, medium, heavy and extra heavy are defined in Table 1 of the above document as follows:

Light:

Areas without industries and with a low density of emission-producing residential heating systems. Areas with some industrial or residential density but subject to frequent winds and/or precipitation. Agricultural areas (exposure to wind-borne fertilizer spray or crop-burning residues can lead to higher contamination levels).Mountainous areas. 

These areas are not exposed to sea winds or located near the sea. Typical measured equivalent salt deposit density (ESDD) levels are 0.03 mg/cm2 to 0.08 mg/cm2.

Medium:

Areas with industries not producing highly polluting smoke and/or with an average density of emission-producing residential heating systems. Areas with high industrial and/or residential density but subject to frequent winds and/or precipitation. Areas exposed to sea winds but not located directly on the coast. Typical measured ESDD levels are 0.08 mg/cm2 to 0.25 mg/cm2.

Heavy:

Areas with high industrial density and large city suburbs with a high density of emission-producing residential heating systems. Areas close to the sea or exposed to strong sea winds. Typical measured ESDD levels are 0.25 mg/cm2 to 0.6 mg/cm2.

Extra heavy:

Small areas subject to industrial smoke-producing thick conductive deposits. Small coastal areas exposed to very strong and polluting sea winds. Typical measured ESDD levels are above 0.6 mg/cm2.

The minimum creep values based on the nominal line to ground kV rating are recommended in the clause 9.1.5 of IEEE Std C57.19.100 as follows:

Contamination          Creep distance

Light                            28 mm/kV

Medium                       35 mm/kV

Heavy                          44 mm/kV

Extra heavy                 54 mm/kV or greater

Below is a list of other measures recommended in the IEEE document to mitigate the risk of flashover in the contaminated areas:

·         Application of protective coating to improve dielectric performance.

·         Installation of conductive glaze bushings.

·         Installation of contamination-resistant composite insulated bushings.

·         Periodic Cleaning of the bushing surface.

·         Design change to minimize the number of outdoor bushings.

Requirements of Line Protection Relay Commissioning

Bilateral (trilateral) protection scheme between any generation station or switching station and the utility station(s) on the other side of the utility transmission line(s) is called tele-protection and is achieved through identical line protection relays at the stations.

In order to ensure compatibility between the stations, it is important that not only the make and model of the relays but also the firmware revision number and its boot revision number is the same, since the boot revision number might be different from the firmware revision number.

The single line diagram, the DC schematics of the line protection relays, as well as a copy of uploaded files to the relays are to be sent to the utility company for approval. At the end of commissioning the as left files shall also be sent to the utility for their approval and records.

Prior to direct transfer trip (DTT) testing, the communications equipment and devices are to be installed and commissioned.  BERT tests (Bit Error Rate Test) are to be conducted to make sure the communication channels are working properly. Then an end to end testing would wrap up the communication tests. 

It is also important to verify that the communication medium and all communication devices such as multiplexers are:

• Capable of working at the data transfer (bit rate) required by the protection relays.
• Have the same fiber optic wavelength.
• All are single mode or multi-mode.

A BERT typically consists of a test pattern generator and a receiver that can be set to the same pattern. They can be used in pairs, with one at either end of a communication chanell, or singularly at one end with a loopback at the remote end.

A loopback test is a test used for debugging physical connection problems in communication channel components in which a signal in sent from a communications device and returned (looped back) to it as a way to identify a failing node in a network. A comparison of the returned signal with the transmitted signal conveys the integrity of the transmission path. One type of loopback test is performed using a special plug, called a Wrap Plug, that is inserted in a port on a communications device.

A wrap plug, also known as a loopback plug, is a special plug that can be inserted into a port on a communications device to perform a diagnostic test called a loopback test. The effect of a wrap plug is to cause transmitted (output) data to be returned as received (input) data, simulating a complete communications circuit using a single computer. There are numerous possible configurations, depending on the hardware and the nature of the test to be performed.

The purpose of the communications channel is to transmit information about the system conditions from one end of the protected line to the other, including requests to initiate or prevent tripping of the remote circuit breaker. The former arrangement is generally known as a 'transfer tripping scheme' while the latter is generally known as a 'blocking scheme'. 

DTT Tests are generally done in two phases:

• Dead Zone Transfer Trip, DZTT
• Live Zone Transfer Trip, LZTT

DZTT is the set of tests done before the energization of the station. During DZTT the trip situations are simulated and signals are sent from either side to verify the intended operation is initiated on the other side. This would verify that the transfer trip equipment are effectively talking to each other and can operate in live conditions.

LZTT is the set of tests implemented after the energization of the station. The signals sent during LZTT actually trip the circuit breaker on each side of the line and de-energize the station and the transmission line.

References:

•          Communication Networks NSD570 – Teleprotection Equipment, ABB
•          SEL-2595 Teleprotection Terminal
•          https://en.wikipedia.org/wiki/Loopback
•          http://searchnetworking.techtarget.com/
•          https://www.techopedia.com/
• 
  
• 
  

CSA Approval Requirements for High Voltage Equipment in Ontario

Canadian Standards Association (CSA) is a non for profit organization accredited for Standard Council of Canada (SCC) to develop Canadian codes and standards. Electrical equipment sold in the market and installed in Ontario shall bear a CSA label which means they have been manufactured and tested according to the relevant CSA standard.

Custom made electrical equipment that are not type tested for mass production, can be factory tested or field tested by CSA, ESA (Electrical Safety Authority in Ontario) or other testing and inspection companies accredited by SCC.

ESA is the electrical safety authority in Ontario responsible for the inspection and approval of all electrical installations in the province.

Conformance with CSA is generally included in the specifications prepared for electrical equipment. However, CSA sticker is not mandatory for high voltage equipment.

For high voltage electrical equipment, the following two provisions are generally included in the specifications in order to meet the code requirements:

1- The high voltage equipment name plate shall include the CSA and/ or other internationally recognized standard the equipment is manufactured and tested to.

2- The control panel(s) shall bear a sticker of an accredited testing facility (CSA or others) to verify the compliance with the applicable CSA standard.

In some cases, the requirement of a CSA blue sticker is added to the purchase order to comply with the second provision above. 

The Blue Sticker indicates that the electric product is tested and meets CSA Group Special Publication SPE-1000. As such, the control panel should have blue sticker otherwise, the product does not meet PO requirement. 

Here is the typical sample of blue sticker affixed on control panel.

CSA Blue sticker is a special inspection label which indicates that the electric, non-healthcare product was tested and has met CSA Group Special Publication SPE-1000, Model Code for the Evaluation of Electrical Equipment, and the Canadian Electrical Code for installations and use. However, the CSA blue sticker is one of the labels that can be used to ensure the control panel meets the relevant code requirements.  

There is a CSA red sticker/ label - shown below- that can also be used for this application. CSA Red sticker is another special inspection label which indicates that the control panel was tested and has met CSA Group Special Publication SPE-1000, Model Code for the Evaluation of Electrical Equipment, and the Canadian Electrical Code for installations and use.

As stated above, there are a number of facilities that can inspect the control panel(s) of high voltage equipment and provide their relevant sticker which would be acceptable by ESA. 

According to ESA product approval card, the recognized certification markings are as follows:

According to the same document the following are the recognized panel-only field evaluation markings:

For example, for any HV transformer installed in Ontario, recognized inspection stickers would be needed for control panel(s) only. As far as the control panel is certified and the transformer nameplate refers to the applicable standards the transformer is built and tested to, the transformer would meet the requirements and will be approved and pass the inspection by the local ESA inspector.

Orange sticker issued by Electrical Safety Authority (ESA), or stickers issued by QPS or Entela depicted above can also be used in lieu of a CSA blue sticker and will be acceptable by local ESA inspector at site.

The certification agencies recognized by ESA are as follows: 

Canadian Standards Association (CSA)Curtis-Straus LLCElectrical Safety Authority Field Evaluation (ESAFE)FM ApprovalsIAPMO R&T, IncIntertek Testing ServicesLab Test Certification IncMet Laboratories Inc. (MET)NemkoNemko CanadaNSF InternationalOMNI Environmental Services Inc.QPSQuality Auditing InstituteSGSTUV AmericaTUV RheinlandUnderwriters Laboratories of Canada (ULC)Underwriters' Laboratories Inc.

The following is the list of field evaluation agencies recognized by ESA. 

Canadian Standards Association (CSA)Electrical Safety Authority Field Evaluation (ESAFE)Intertek Testing ServicesLab Test Certification IncMet Laboratories Inc. (MET)NemkoQPSQuality Auditing InstituteTUV AmericaTUV RheinlandUnderwriters Laboratories of Canada (ULC)

References:

  -  ESA Bulletin 36-1-21

  -  CSA Website: http://www.csagroup.org/services-industries/marks-labels/csa-marks/

  -  Standard Council of Canada Website: https://www.scc.ca/