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/
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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/

NERC Requirements for Generation Stations

There are number of standards where NERC (North American Electricity Reliability Corporation) dictates specific requirements for the equipment, protection, control and operation of the transmission facilities. The below NERC standards can be referred to for this specific requirement: 

·         NERC PRC 023-2 (Transmission Relay Loadability)

·         NERC FAC-008-3 (Facility Ratings)

·         NERC PRC-025-1 (Generator Relay Loadability)

Although the current industry accepted design based on transmission code -referred to as "Good Utility Practice"- would inherently meet normal NERC requirements, the Engineer shall ensure all the requirements are met since the Client (Generator) would be subject to a NERC audit for compliance after the installation and commissioning of the generation station. 

The Engineer, needs to focus on the design requirements. However, there are more operational requirements that the Generator shall be responsible for and shall be taken into account. In other words, once the Engineer's design meets NERC requirements for reliability, that is where their obligations end.

The existing facilities that do not comply with the latest NERC requirements are allowed to continue to operate. But any major retrofit project or expansion to the existing facilities shall include additional equipment / systems to comply with the new requirements.

Our engineering and design of stations in Ontario -which is based on Ontario Energy Board's Transmission System Code- generally complies with NERC requirements. Two important aspects of generation stations that are mandatory and need to be taken into account during the initial estimate and subsequent design are as follows:    

1- There shall be two battery banks for protection and control equipment. Unlike load stations one common battery bank with two chargers would not be acceptable for generation stations.

2- There shall be a circuit breaker for switching at the switching station. Unlike load stations motorized disconnect switch would not suffice.

Those are the major two features that affect the generation stations. Other NERC requirements shall be similar to those of load stations and would not have a significant impact on the project estimate and the design.

The concern here for generation stations in wind power projects is that while in some cases the generators are derated to suit project requirements, NERC PRC 023-2 and NERC PRC-025-1 require 150% setting on transmission, transformer protection, 130% of rated nameplate of the generator (not de-rated).

This shall be dealt with closely as it could mean that the station and collector system shall be so designed to carry nameplate rated load. This will have a huge impact on the equipment while it can never happen in practice.

In wind generation facilities, loadability is limited by inherent current-limit in WTG's and the cables / transformers will not be overloaded however the relays are generally set to 10%-15% above maximum load per worst case scenario identified in the power flow study and fault overcurrent protections would be based on the fault fed from the grid. If WTG's are derated and the derated MVA has been the base for the design of stepup transformers and the collector cables, then the settings have to be selected for derated equipment loadability again by the power flow study.

The NERC standard has observation to synchronizing generator plants and transmission grid loadability which have 130% generation capability. In wind power projects with Type-4 Generator / Inverters, each generator is able to run up to 105% of its nominal rating then a 130% setting is not effective. If the design is based on /contracted for the derated WTG then the system is registered / recognized to the utility for the derated MVA not nominal generator MVA. Regardless, the generation is limited by generator manufacturer’s setting to the derated MVA.

If the generation is comparable to the grid MVA at the POI (point of interconnection), then the system stability is critical and loadability is important. In most of windfarm projects the source is considered weak-infeed and has no impact on stability then the loadability is more important to the client as profitability!    

links:
http://www.nerc.com/pa/Stand/Reliability%20Standards/PRC-025-1.pdf

http://www.nerc.com/pa/Stand/Project%202010132%20Phase%202%20Relay%20Loadability%20Generati/PRC_023_3_Transmission_Relay_Loadability_2013_06_20_Draft_3_(Clean).pdf

HEAT ILLNESS

Have you ever worked in outdoor substations in summer time? How about indoor electrical rooms with no air conditioning equipment in hot and humid summer? The situation would be worse when high humidity adds to high temperature in the work place. 

Common perception is that the body cools itself by sweating. This is true; however, it is only part of the fact. Your sweat needs to evaporate from your skin to make your body cool down. During hot weather, with high humidity, sweating isn't enough, since it doesn’t evaporate. Body temperature can rise to dangerous levels if you don't drink enough water and rest in the shade. You can suffer from heat exhaustion or heat stroke.

According to OSHA (Occupational Safety and Health Administration), in 2014 alone, 2,630 workers suffered from heat illness and 18 died from heat stroke and related causes on the job in the United States. 

OSHA recommends the following measures to mitigate the risk of heat illness in work place:

·        Drink water every 15 minutes, even if you are not thirsty.

·        Rest in the shade to cool down.

·        Wear a hat and light-colored clothing.

·        Learn the signs of heat illness and what to do in an emergency.

·        Keep an eye on fellow workers.

·        "Easy does it" on your first days of work in the heat. You need to get used to it.

 And here’s OSHA’s chart for symptoms and first aid measures to take if a worker shows signs of a heat-related illness:

Illness	Symptoms	First Aid*
Heat stroke	Confusion Fainting Seizures Excessive sweating or red, hot, dry skin Very high body temperature	Call 911 While waiting for help: Place worker in shady, cool area Loosen clothing, remove outer clothing Fan air on worker; cold packs in armpits Wet worker with cool water; apply ice packs, cool compresses, or ice if available Provide fluids (preferably water) as soon as possible Stay with worker until help arrives
Heat exhaustion	Cool, moist skin Heavy sweating Headache Nausea or vomiting Dizziness Light headedness Weakness Thirst Irritability Fast heart beat	Have worker sit or lie down in a cool, shady area Give worker plenty of water or other cool beverages to drink Cool worker with cold compresses/ice packs Take to clinic or emergency room for medical evaluation or treatment if signs or symptoms worsen or do not improve within 60 minutes. Do not return to work that day
Heat cramps	Muscle spasms Pain Usually in abdomen, arms, or legs	Have worker rest in shady, cool area Worker should drink water or other cool beverages Wait a few hours before allowing worker to return to strenuous work Have worker seek medical attention if cramps don't go away
Heat rash	Clusters of red bumps on skin Often appears on neck, upper chest, folds of skin	Try to work in a cooler, less humid environment when possible Keep the affected area dry
* Remember, if you are not a medical professional, use this information as a guide only to help workers in need.

Refer to OSHA’s website for further information at the following link:

 https://www.osha.gov/SLTC/heatstress/heat_illnesses.html