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