A Short-term Interruption In Electrical Power Availability Is Known As A ____.

Interruptions happen more often in these areas, and for longer times. Again, a UPS/battery backup helps protect you against a complete loss of power. Short-term Variations. Short-term variations, known as sags and swells, can last milliseconds and create a drain on your power.

A diesel generator (DG) (also known as diesel genset) is the combination of a diesel engine with an electric generator (often an alternator) to generate electrical energy. This is a specific case of engine-generator. A diesel compression-ignition engine is usually designed to run on diesel fuel, but some types are adapted for other liquid fuels or natural gas.

Diesel generating sets are used in places without connection to a power grid, or as emergency power-supply if the grid fails, as well as for more complex applications such as peak-lopping, grid support and export to the power grid.

Proper sizing of diesel generators is critical to avoid low-load or a shortage of power. Sizing is complicated by the characteristics of modern electronics, specifically non-linear loads. In size ranges around 50 MW and above, an open cycle gas turbine is more efficient at full load than an array of diesel engines, and far more compact, with comparable capital costs; but for regular part-loading, even at these power levels, diesel arrays are sometimes preferred to open cycle gas turbines, due to their superior efficiencies.

Diesel generator set[edit]

The packaged combination of a diesel engine, a generator and various ancillary devices (such as base, canopy, sound attenuation, control systems, circuit breakers, jacket water heaters and starting system) is referred to as a 'generating set' or a 'genset' for short.

Set sizes range from 8 to 30 kW (also 8 to 30 kVA single phase) for homes, small shops and offices with the larger industrial generators from 8 kW (11 kVA) up to 2,000 kW (2,500 kVA three phase) used for large office complexes, factories, and other industrial facilities. A 2,000 kW set can be housed in a 40 ft (12 m) ISO container with fuel tank, controls, power distribution equipment and all other equipment needed to operate as a standalone power station or as a standby backup to grid power. These units, referred to as power modules, are gensets on large triple axle trailers weighing 85,000 pounds (38,555 kg) or more. A combination of these modules are used for small power stations and these may use from one to 20 units per power section and these sections can be combined to involve hundreds of power modules. In these larger sizes the power module (engine and generator) are brought to site on trailers separately and are connected together with large cables and a control cable to form a complete synchronized power plant.A number of options also exist to tailor specific needs, including control panels for autostart and mains paralleling, acoustic canopies for fixed or mobile applications, ventilation equipment, fuel supply systems, exhaust systems, etc.

Diesel generators are not only for emergency power, but may also have a secondary function of feeding power to utility grids either during peak periods, or periods when there is a shortage of large power generators. In the UK, this program is run by the national grid and is called STOR.

Ships often also employ diesel generators, sometimes not only to provide auxiliary power for lights, fans, winches etc., but also indirectly for main propulsion. With electric propulsion the generators can be placed in a convenient position, to allow more cargo to be carried. Electric drives for ships were developed before World War I. Electric drives were specified in many warships built during World War II because manufacturing capacity for large reduction gears was in short supply, compared to capacity for manufacture of electrical equipment.^[1] Such a diesel-electric arrangement is also used in some very large land vehicles such as railroadlocomotives.

Generator size[edit]

Generating sets are selected based on the electrical load they are intended to supply, the electrical load's characteristics such as kW, kVA, var, harmonic content, surge currents (e.g., motor starting current) and non-linear loads. The expected duty (such as emergency, prime or continuous power) as well as environmental conditions (such as altitude, temperature and exhaust emissions regulations) must also be considered.

Most of the larger generator set manufacturers offer software that will perform the complicated sizing calculations by simply inputting site conditions and connected electrical load characteristics.

Power plants – electrical 'island' mode[edit]

One or more diesel generators operating without a connection to an electrical grid are referred to as operating in island mode. Operating generators in parallel provides the advantage of redundancy, and can provide better efficiency at partial loads. The plant brings generator sets online and takes them off line depending on the demands of the system at a given time. An islanded power plant intended for primary power source of an isolated community will often have at least three diesel generators, any two of which are rated to carry the required load. Groups of up to 20 are not uncommon.

Generators can be electrically connected together through the process of synchronization. Synchronization involves matching voltage, frequency and phase before connecting the generator to the system. Failure to synchronize before connection could cause a high short circuitcurrent or wear and tear on the generator or its switchgear. The synchronization process can be done automatically by an auto-synchronizer module, or manually by the instructed operator. The auto-synchronizer will read the voltage, frequency and phase parameters from the generator and busbar voltages, while regulating the speed through the engine governor or ECM (Engine Control Module).

Load can be shared among parallel running generators through load sharing. Load sharing can be achieved by using droop speed control controlled by the frequency at the generator, while it constantly adjusts the engine fuel control to shift load to and from the remaining power sources. A diesel generator will take more load when the fuel supply to its combustion system is increased, while load is released if fuel supply is decreased.

Supporting main utility grids[edit]

In addition to their well known role as power supplies during power failures, diesel generator sets also routinely support main power grids worldwide in two distinct ways:

Grid support[edit]

Emergency standby diesel generators, such as those used in hospitals and water plants, are, as a secondary function, widely used in the US and, in the recent past, in Great Britain to support the respective national grids at times for a variety of reasons. In the UK the tenders known as the Short Term Operating Reserve have exhibited quite variable prices, and from 2012 the volume of demand-side participation, which mainly entails the use of on-site diesels, has dropped as the tendered prices fell. Some 0.5 GWe of diesels have at times been used to support the National Grid, whose peak load is about 60 GW. These are sets in the size range 200 kW to 2 MW. This usually occurs during, for example, the sudden loss of a large conventional 660 MW plant, or a sudden unexpected rise in power demand eroding the normal spinning reserve available.^[2]

This is beneficial for both parties - the diesels have already been purchased for other reasons; but to be reliable need to be fully load tested. Grid paralleling is a convenient way of doing this. This method of operation is normally undertaken by a third party aggregator who manages the operation of the generators and the interaction with the system operator.

These diesels can in some cases be up and running in parallel as quickly as two minutes, with no impact on the site (the office or factory need not shut down). This is far quicker than a base load power station which can take 12 hours from cold, and faster than a gas turbine, which can take several minutes. Whilst diesels are very expensive in fuel terms, they are only used a few hundred hours per year in this duty, and their availability can prevent the need for base load station running inefficiently at part load continuously. The diesel fuel used is fuel that would have been used in testing anyway.

In Great Britain, National Grid can generally rely upon about 2 GW of customer demand reduction via back-up diesels being self-dispatched for about 10 to 40 hours a year at times of expected peak national demand. National Grid does not control these diesels - they are run by the customer to avoid 'triad' transmission network use of system (TNUoS) charges which are levied only on consumption of each site, at the three half-hours of peak national demand. It is not known in advance when the three half-hours of peak national demand (the 'triad' periods) will be, so the customer must run his diesels for a good deal more half-hours a year than just three.

The total capacity of reliably operable standby generation in Britain is estimated to be around 20 GW, nearly all of which is driven by diesel engines. This is equivalent to nearly 29% of the British system peak, although only a very small fraction will ever be generating at the same time. Most plant is for large offices blocks, hospitals, supermarkets, and various installations where continuous power is important such as airports. Therefore, most is in urban areas, particularly city and commercial centres. It is estimated that around 10% of plant exceeds 1 MW, about 50% is in the 200 kW-1 MW range, and the remaining 40% is sub-200 kW. Although it is growing, only a very small proportion is believed to be used regularly for peak lopping, the vast majority just being only for standby generation. The information in this paragraph is sourced from section 6.9 of the government report : 'Overcoming Barriers To Scheduling Embedded Generation To Support Distribution Networks'^[3]

Increasing use of banks of diesel generators (known as 'diesel farms') is being made in Britain to balance the fluctuating output from renewable energy sources, such as wind farms.^[4]

A similar system to Great Britain's Short Term Operating Reserve operates in France. It is known as EJP; at times of grid stress, special tariffs can mobilize at least 5 GW of diesel generating sets to become available. In this case, the diesels prime function is to feed power into the grid.

During normal operation in synchronization with the electricity net, powerplants are governed with a five percent droop speed control. This means the full load speed is 100% and the no load speed is 105%. This is required for the stable operation of the net without hunting and dropouts of power plants. Normally the changes in speed are minor. Adjustments in power output are made by slowly raising the droop curve by increasing the spring pressure on a centrifugal governor. Generally this is a basic system requirement for all powerplants because the older and newer plants have to be compatible in response to the instantaneous changes in frequency without depending on outside communication.^[5]

Cost of generating electricity[edit]

Typical operating costs[edit]

Fuel consumption is the major portion of diesel plant owning and operating cost for power applications, whereas capital cost is the primary concern for backup generators. Specific consumption varies, but a modern diesel plant will, at its near-optimal 65-70% loading, generate at least 3 kWh per litre (ca. 30% fuel efficiency ratio).^[6][7]

Generator sizing and rating[edit]

Rating[edit]

Generators must provide the anticipated power required reliably and without damage and this is achieved by the manufacturer giving one or more ratings to a specific generator set model. A specific model of a generator operated as a standby generator may only need to operate for a few hours per year, but the same model operated as a prime power generator must operate continuously. When running, the standby generator may be operated with a specified - e.g. 10% overload that can be tolerated for the expected short running time. The same model generator will carry a higher rating for standby service than it will for continuous duty. Manufacturers give each set a rating based on internationally agreed definitions.

These standard rating definitions are designed to allow valid comparisons among manufacturers, to prevent manufacturers from misrating their machines, and to guide designers.

Generator Rating Definitions

Standby Rating based on Applicable for supplying emergency power for the duration of normal power interruption. No sustained overload capability is available for this rating. (Equivalent to Fuel Stop Power in accordance with ISO3046, AS2789, DIN6271 and BS5514). Nominally rated.

Typical application - emergency power plant in hospitals, offices, factories etc. Not connected to grid.

Prime (Unlimited Running Time) Rating: Should not be used for Construction Power applications. Output available with varying load for an unlimited time. Typical peak demand 100% of prime-rated ekW with 10% of overload capability for emergency use for a maximum of 1 hour in 12.^{[citation needed]} A 10% overload capability is available for limited time. (Equivalent to Prime Power in accordance with ISO8528 and Overload Power in accordance with ISO3046, AS2789, DIN6271, and BS5514). This rating is not applicable to all generator set models.

Typical application - where the generator is the sole source of power for say a remote mining or construction site, fairground, festival etc.

Base Load (Continuous) Rating based on: Applicable for supplying power continuously to a constant load up to the full output rating for unlimited hours. No sustained overload capability is available for this rating. Consult authorized distributor for rating. (Equivalent to Continuous Power in accordance with ISO8528, ISO3046, AS2789, DIN6271, and BS5514). This rating is not applicable to all generator set models

Typical application - a generator running a continuous unvarying load, or paralleled with the mains and continuously feeding power at the maximum permissible level 8,760 hours per year. This also applies to sets used for peak shaving /grid support even though this may only occur for say 200 hours per year.

As an example if in a particular set the Standby Rating were 1000 kW, then a Prime Power rating might be 850 kW, and the Continuous Rating 800 kW. However these ratings vary according to manufacturer and should be taken from the manufacturer's data sheet.

Often a set might be given all three ratings stamped on the data plate, but sometimes it may have only a standby rating, or only a prime rating.

Sizing[edit]

Typically however it is the size of the maximum load that has to be connected and the acceptable maximum voltage drop which determines the set size, not the ratings themselves. If the set is required to start motors, then the set will have to be at least three times the largest motor, which is normally started first. This means it will be unlikely to operate at anywhere near the ratings of the chosen set.

Many gen-set manufacturers have software programs that enable the correct choice of set for any given load combination. Sizing is based on site conditions and the type of appliances, equipment, and devices that will be powered by the generator set.^[8]

Fuels[edit]

Diesel fuel is named after diesel engines, and not vice versa; diesel engines are simply compression-ignition engines, and can operate on a variety of different fuels, depending on configuration and location. Where a gas grid connection is available, gas is often used, as the gas grid will remain pressurized during almost all power cuts. This is implemented by introducing gas with the intake air and using a small amount of diesel fuel for ignition. Conversion to 100% diesel fuel operation can be achieved instantaneously.^[9]

In more rural situations, or for low load factor plant, diesel fuel derived from crude oil is a common fuel; it is less likely to freeze than heavier oils. Endurance will be limited by tank size. Diesel engines can work with the full spectrum of crude oil distillates, from natural gas, alcohols, gasoline, wood gas to the fuel oils from diesel oil to cheaper residual fuels that are like lard at room temperature, and must be heated to enable them to flow down a fuel line.^[10]

Larger engines (from about 3 MWe to 30 MWe) sometimes use heavy oils, essentially tars, derived from the end of the refining process. The slight added complexity of keeping the fuel oil heated to enable it to flow, whilst mitigating the fire risks that come from over-heating fuel, make these fuels unpopular for smaller, often unmanned, generating stations.

Other possible fuels include: biodiesel, straight vegetable oil, animal fats and tallows, glycerine, and coal-water slurry. These should be used with caution and due to the composistion, normally have a detrimental effect on engine life.

See also[edit]

• Calculating the cost of the UK Transmission network: cost per kWh of transmission
• Calculating the cost of back up: See spark spread

References[edit]

1. ^[1]Archived November 7, 2008, at the Wayback Machine
2. ^'Short Term Operating Reserve (STOR)'. nationalgrideso.com. Retrieved 2012-07-13.
3. ^'Overcoming Barriers To Scheduling Embedded Generation To Support Distribution Networks'(PDF). BERR. Archived from the original(PDF) on 2010-03-04. Retrieved 2014-07-15.
4. ^https://www.theguardian.com/business/2016/dec/06/diesel-farms-national-grid-tax-breaks
5. ^Speed Droop and Power Generation. Application Note 01302. 2. Woodward. Speed
6. ^'Cummins Power Generation : Model DGDB'(PDF). Cumminspower.com. Retrieved 2013-10-28.
7. ^'Approximate Diesel Generator Fuel Consumption Chart'. Dieselserviceandsupply.com. Retrieved 2012-07-13.
8. ^'basic sizing of diesel generators'. wellandpower.net. Retrieved 2019-06-03.
9. ^'Low Speed Engines'. Manbw.com. 2008-11-19. Retrieved 2009-05-11.
10. ^'Dual-fuel-electric LNG carriers'(PDF). Thedigitalship.com. Archived from the original(PDF) on 2011-06-26. Retrieved 2013-10-28.

1. Preparing for an Electrical Power Outage. Pre-planning reduces business interruption risks. A blackout is a momentary or prolonged loss of power. A blackout can result in lost or corrupted data, failures of process control equipment, and loss of products or services. A brownout is a significant voltage reduction which results in similar problems.
2. A short-term interruption in electrical power availability is known as a fault. The fault is the abnormal condition of the electrical system. Breakdown due to insulation and abnormal voltages caused by switching surges or lightning strokes are some of the triggers for faults.

A Short-term Interruption In Electrical Power Availability Is Known As A ____

Advice for planning, design, installation, inspection, maintenance and more

Health care facility power systems are required to operate dependably, with high reliability and availability. They must operate and give the same results on successive trials as well as function at any instant required and from that point forward.

Best practices can be undertaken throughout the life cycle of power systems. The power system life cycle starts with planning, design, construction, installation and commissioning. It then continues with ongoing inspection, testing and maintenance. Existing power systems may have unknown vulnerabilities that can be uncovered and removed or mitigated. And, finally, management of the power systems should include identifying preferred failure responses and planning appropriately for them.

Interruptions occur when the supply voltage decreases to 10 percent or less of nominal. Voltage transients, also known as impulses, are rapid, short-term voltage increases that are categorized as either impulsive (large, short-term waveform deviation) or oscillatory (ringing signal following initial transient).

This, of course, is in addition to codes, standards or accreditation-related compliance requirements.

System installation

Many of the best practices for high-reliability designs are well-known but not always attainable because of cost — minimizing physical risks due to environmental causes such as flooding, windborne hazards and other potential hazards. Protection from flooding should consider both external (such as inclement weather) and internal (such as a broken pipe or tank in a nearby mechanical room) causes. Health facilities professionals also should consider that water is almost always likely to find the lowest elevation and a sump pump is only as good as its power source and maintenance.

Despite best efforts, power equipment sometimes fails. Installing power systems that mitigate the impact of discrete equipment failures can be a best practice that allows rapid response for isolation and repair of failed equipment. Examples are power systems with multiple electrical utility feeds as well as main and tie device arrangements that can be switched automatically, manually or both. The adverse impact of incoming utility service failures also might be mitigated if the facility power system contains means to connect portable equipment such as generator sets. All portable equipment connections also should be designed considering electrical safety.

Other best practices include both physical separation and fire separation between normal power equipment and emergency power equipment, and limitations on possible equipment locations to those that are at less risk to adverse environmental influences. Sometimes further separation between similar systems (normal power “A” and normal power “B” for example) also can be considered a best practice to reduce the potential for putting all eggs in one basket.

Power equipment design choices also can encompass best practices by specifying equipment details that facilitate ongoing inspection, testing and maintenance. Modern power system equipment contains many features that can be used to maintain or improve dependability.

For example, infrared viewports can be installed within the outer enclosures of power equipment. These viewports allow regular infrared thermographic scanning of interior components to be performed without the risk of opening the covers of energized equipment. Likewise, manufacturer-recommended maintenance of emergency power automatic transfer switches (a National Fire Protection Association NFPA 110 requirement) is facilitated when the automatic transfer switches are bypass-isolation design. The bypass-isolation design is intended to permit the electromechanical transfer mechanism to be maintained without causing a power outage of its high-priority loads. Additionally, electrical power switchgear can be provided with special features to improve electrical safety during equipment testing and maintenance.

Commissioning is recommended whenever power system components are installed or modified. The purpose of commissioning, which goes beyond the typical design team construction observation and punch list process, is to ensure that the power system installation is in accordance with the contract documents and the owner’s project requirements. Some power equipment failures were traced to deficiencies that could have been found and corrected by a comprehensive, commissioning and installation acceptance testing process.

Finally, design projects commonly result in good documentation of system configuration; however, hospitals usually have many changes over time. The overlapping quilt of infrastructure changes over years will make even the best construction drawings outdated and, thus, not very usable for operational needs. A best practice is to maintain current documentation of the information necessary for operational needs such as internal system failure response.

Proactively determining the changing load on major power equipment as the facility evolves is a best practice. There are many ways to do this, including power monitoring systems, portable metering and load profile analyses.

Maintaining performance

Regular inspection of high-value electrical equipment is important. It allows the operational staff to determine whether adverse environmental changes or equipment changes have occurred that should be corrected to maintain desired reliability. Facilities personnel are the eyes and ears of the organization; through regular rigorous inspection protocols, they are more likely to find potential environmental and equipment problems before equipment failures occur.

As the demands upon our facilities change, the power systems may not always change with them. Many hospitals operate with power equipment that is decades past its useful life. In those cases, enhanced inspection and maintenance are critical to continued dependable operation.

Management of portions of the power system, such as the emergency power supply systems, must meet the minimum inspection, testing and maintenance requirements stipulated in NFPA 110, Standard for Emergency and Standby Power Systems. For the normal power systems along with other utilities, however, the Centers for Medicare & Medicaid Services (CMS) now also requires that organizations know the manufacturer’s recommended maintenance activities and frequencies. The organizations are required to conduct a risk-based analysis to justify deviating from those recommendations.

Annual infrared thermographic scanning of electrical power equipment is a best practice. It helps organizations to discover potential problem areas and correct them before they develop into dangerous and disruptive failures. It also can be used as a predictive maintenance tool to help focus limited funding.

Electrical power equipment maintenance is a best practice, but is hard to accomplish within health care facilities. The 2012 American Society for Healthcare Engineering (ASHE) management monograph titled “Managing Hospital Electrical Shutdowns” contains a robust discussion of issues and recommendations related to this topic. Other recommended actions include:

Planning for contingencies. Although most hospitals have some form of utility equipment failure procedures, a best practice can be validating that the failure procedures will pass the responding staff member’s reality test the day the failure occurs.

Many power failure procedures simply assume the loss of incoming utility service. Although this assumption certainly has a major impact on the facility, it is not the most common example of a power failure experienced within hospitals. Power system-related failures are more commonly a malfunctioning component such as a transfer switch, a short circuit within a feeder due to construction or other damage, a lighting ballast failure that trips out a major riser to multiple floors, or any other failure that results in the loss of one or more panelboards, motor control centers or switchboards.

A best practice is to recognize that these internal failures happen and plan appropriate responses ahead of time. Consider the different failure points, not just at the electrical service mains. The failure responses should be different for each type of failure, and it is too late to formulate a response after the failure.

Finding and mitigating vulnerabilities. There are many available activities that can have a positive impact on the dependability of existing power system installations. Facility personnel can find power system vulnerabilities by assessing their physical installations, operations, training, communications, inspections, testing, maintenance, electrical safety, contingency planning and hidden common-mode failure potential for their effect on reliability, availability and dependability.

Options for reviewing and improving the dependability of existing installations can include conducting risk assessments, identifying existing or potential hazards and undertaking hazard mitigation strategies.

An example of proactive inspection resulting in identification of vulnerabilities includes:

• Visiting the facility’s high-value electrical equipment rooms, such as those containing emergency power equipment or main normal power electrical service equipment.

• Determining whether any of those rooms are adjacent to mechanical rooms and whether it is possible for water to enter the electrical rooms if any of the mechanical pipes or tanks leak or break.

• Determining whether electrical rooms on lower floors are subject to external flooding in certain situations.

Facilities professionals should consider using leak detection in the high-value electrical rooms, which warn of water-based vulnerabilities. The leak detection equipment should be monitored and subject to its own inspection, testing and maintenance processes.

Another simple example is one in which the organization relies on sump pumps to protect critical equipment or processes. Facilities professionals should check whether the sump pumps themselves have been looked at as a potential vulnerability upon failure. Additionally, they should check whether the sump pumps are monitored and whether they are included in any inspection, testing and maintenance processes.

Assessing failure risks. Risk assessments are used regularly where required in many aspects of the health care physical environment. They are not often used, however, to assess existing power systems, where they may be considered to be a best practice. Examples of power system risk-assessment topics can include:

• Locations of normal power equipment;

• Locations of emergency power equipment;

• Whether to upgrade or replace older equipment;

• Assessing potential vulnerabilities that have been discovered;

• Determining the need for more robust utility failure procedures;

• Whether to provide emergency power (beyond regulatory requirements) to certain mechanical equipment;

• Inspection, testing and maintenance options beyond regulatory requirements.

• Analyzing vulnerabilities. Power system vulnerability analyses are a best practice and can be used in many ways. For example, vulnerability analyses can be used to determine what types of loads that are presently powered only by normal power should be powered from emergency power.

A vulnerability analysis can be used to identify the importance of findings and observations from ongoing inspection, testing and maintenance activities.

Vulnerability analyses also can assist in identifying the potential for common-mode failures, which are failures of two or more systems or components due to a single event or cause. A safety engineering concept states that once a failure mode is identified, it usually can be mitigated by adding extra or redundant equipment to the system. However, the existence of an uncorrected common-mode failure potential removes the advantage of other redundancies. Examples of potential common-mode failure points in an emergency power system are a single fuel storage tank, a common fuel oil riser pipe, or even a single fuel oil pump control panel.

When looking for potential vulnerabilities, consider that things break. Just because equipment worked well yesterday does not mean that it will work well tomorrow. Pay attention to the details — often those details can result in unexpected occurrences. When failures occur, look for any commonalities that suggest system issues or process issues rather than just single failures. Remember that you can’t control what you can’t control, so you should plan for the unwanted. Have rigorous failure procedures that can be understood and followed by those who may need to respond.

Analyzing performance gaps. Many hospitals employed gap analyses to assess what equipment was powered by emergency power and whether there were gaps in the selection of power sources that needed to be corrected. This approach was somewhat common among Joint Commission-accredited hospitals after it issued its 2006 Sentinel Event Alert, Issue 37 titled “Preventing adverse events caused by emergency electrical power system failures.”

Gap analyses can be a structured approach to assessing any problematic situation and developing solutions to rectify the problem areas. As a best practice, a gap analysis also can be used to address the results of a vulnerability analysis. This can assist organizations in formalizing an action plan to assess specific vulnerabilities, the types of failures that might be caused by those vulnerabilities, and how the vulnerabilities can be eliminated or reduced.

A gap analysis can be structured as the following action-oriented process:

• Define the concerns, policies, urgency, needed data and metrics;

• Assess the current situation;

• Analyze data and summarize gaps;

• Develop recommended actions to close the gaps;

• Brainstorm strategies to bridge gaps and recommendations;

• Determine the best short-term and long-term options;

• Develop action plans;

• Implement the action plans.

Finally, it can be helpful to understand the vulnerability management life cycle. This includes finding potential vulnerabilities, prioritizing their potential likelihood and effect, assessing their impact on operations and patient care, reporting the results, taking short-term and long-term actions to mitigate the impact, and then verifying that the actions taken really mitigated the vulnerability.

Important function

Many of these best practices are covered in the 2014 ASHE management monograph titled “Managing Hospital Emergency Power Systems: Testing, Operation, Maintenance, Vulnerability Mitigation, and Power Failure Planning.” But, regardless of the source, ensuring emergency power reliability is among a facilities professional’s most important functions.

David Stymiest, PE, CHFM, CHSP, FASHE, is a senior consultant at Smith Seckman Reid, Nashville, Tenn., specializing in independent review of power systems, facilities engineering and regulatory compliance. Although he is chair of the NFPA Technical Committee on Emergency Power Supplies, which is responsible for NFPA 110 and 111, the views and opinions expressed shall not be considered the official position of NFPA or any of its technical committees and shall not be considered to be, nor be relied upon as, a formal interpretation. He can be reached at DStymiest@SSR-inc.com.

Educating clinicians about emergency backup

Lessons learned during recent major disasters indicate that many clinicians have unrealistic expectations about normal and emergency power failures. A best practice is for facilities professionals to educate clinicians about different power failure modes and the necessary responses to each.

The education should be comprehensive enough so that clinicians understand the different potential types of electrical failure in any critical care unit, each with its own response. These include:

• Failure of some portions of the normal power system with the remainder of the normal power still online and the emergency power system, also called the essential electrical system (EES), also available;

• Failure of the entire normal power system with the EES still online;

• Failure of one or more of the EES branches (e.g., life safety branch, critical branch or equipment branch) with the normal power system still online;

• In critical care spaces that have two separate critical branch sources, failure of one of the two critical branches with the other critical branch source still online;

• Total electrical failure to the space, either simultaneously or as the result of cascading failures over a period of time.

With each of these failure scenarios, the resulting impact on activities and required actions by caregivers may be different. Whereas, the most common anticipated response to a utility service outage is ensuring that critical equipment is plugged into emergency power (red) outlets, the actual requirement in the event of a critical branch failure would be to unplug equipment from the red outlets and plug it into the alternative outlets. Quickly differentiating between different scenarios and their necessary responses can improve patient care and patient safety when adverse power conditions occur.

Power outages come in many shapes and forms, and can be local, regional or widespread. One of the best ways to minimize damage from any of these forms is to immediately switch to your own power source—at least for the short term.

At the local level, you can pay (often quite a lot) for your local utility to run a second line to your business. Located as far away as possible from the main line, the second line will lower the odds that both lines are damaged by the same physical event. Also, be sure your on-site electrical distribution equipment is properly maintained. Problems with this equipment can cause more than their share of outages.

To protect against common short-term dips and spikes, consider uninterruptible power supplies (UPS). A standard feature in many data centers, a UPS uses stored energy to bridge the short gap between when an outage hits and when you’re able to switch to another power source or, at least, to properly shut down equipment. For longer outages, on-site emergency generators can supply power for as long as their fuel lasts--but they can’t come on line nearly as fast as a UPS.

Finally, distributed power equipment/cogeneration systems provide substantial, proactive protection. Similar to an emergency or backup power generator, these systems are intended to be run regularly and not just during outages. Companies often use them regularly during hours of peak demand or peak electrical cost to preempt possible brownouts while lowering costs.