Co-founder and Chief Business Development Officer, Claroty, New York

BS Computer Science, York University, Toronto; MBA, International Institute of Management and Development, Switzerland Galina Antova graduated from York University in Toronto before getting her MBA at IMD in Switzerland. She has made impacts in her professional career with IBM and Siemens. Most recently, Galina founded Claroty, a holistic cybersecurity platform. "I chose this career path because I believe that there is no more important work in the field of cybersecurity than ensuring the safety and security of the networks that power the world's critical infrastructure.” Founded in 2014, Claroty, under the leadership of Galina, has become one of the most comprehensive OT security platforms. Galina has also been a strong proponent of the advancement of women in technology, spending much of her time mentoring women in this field. She is even an “Activator” with SheEO, a global initiative focused on building an innovative new model to finance, support, and celebrate female entrepreneurs. As a lover of history and culture, Galina makes it a point to immerse herself in these pursuits wherever her work and travels take her. Her company presented on ICS Security at DEF CON 25 in July 2017.]]>

- Review design issues that impact backup, standby, and emergency power.
- Know the codes and standards that outline the requirements for system design.
- Assess generator systems and the various types that can be specified.

When all other power systems fail in buildings, generators are the workhorses that are expected to operate rapidly and reliably. It is critical for design professionals to have a thorough understanding of proper generator system design. For the generator system to be the “last line of defense,” designers must follow a systematic approach to determine the design criteria, make system selections, and provide a constructible and code-compliant design to construction. This article will highlight design issues that have impacted the author or have been identified by generator manufacturers as “frequent misses” in designs. At the end of the article, we will review how these key design elements were applied to a generator installation at a medical facility.

- NFPA 70-2017: National Electrical Code (NEC). Many sections of the NEC apply to a generator installation. However, Articles 445 (Generators), 517 (Health Care Facilities), 700 (Emergency Systems), 701 (Legally Required Standby Systems), 702 (Optional Standby Systems), 705 (Interconnected Electric Power Production Sources), and 708 Critical Operations Power Systems (COPS) require special attention.
- NFPA 99-2015: Health Care Facilities Code.
- NFPA 101-2015: Life Safety Code.
- NFPA 110-2016: Standard for Emergency and Standby Power Systems.
- Mission Critical Installations:

- Uptime Institute Standards

- TIA 942: Telecommunications Infrastructure Standard for Data Centers.

- ISO 8528-1: Reciprocating Internal Combustion Engine Driven Alternating Current Generating Sets.

- What type of building will this serve? Will this be used for a mission critical application, hospital, industrial facility, or another type of load? The answers here will determine the codes and standards that apply to the design.
- How will the generator be used? For example:

- Is it used as backup power in the event of utility failure or will it provide power continuously throughout the year?

- How will the generator be operated? Is it a 100% standby application or will the onsite staff start the generator during rate curtailment or during a storm event?

- Will the loads be emergency, legally required, or optional standby as classified in Articles 700, 701, and 702 of the NEC? - Site conditions:

- Ambient conditions: What is the maximum temperature of the cooling air as it enters the machine? National Electrical Manufacturers Association (NEMA) ratings are based on 104°F, so if the installation exceeds those limits, let the manufacturer know. Derating will be required.

- Altitude: Generators operating at about 3,281 ft. may need to be derated. Make sure to provide the altitude of the site to the generator manufacturer and take altitude into account when performing load calculations. Most manufacturers can provide derating factors for a given altitude.

- Are there any other site conditions that will impact generator operation, such as a corrosive environment, excessive humidity, or extreme cold

- They are permanently installed.
- Are used to back up permanently installed utility service.
- Only run during a power outage/loss of utility service.

- Locate inlets and exhaust away from each other and other sources of heat.
- Avoid stagnant air or entrainment of other exhaust streams.
- Exhaust the generator from the highest point of the installation.
- For outdoor installations, avoid installing generator systems in completely enclosed areas.
- For multiple-generator applications, model the airflow with all engines running and a partial set of engines running. The airflow internal to the room will be different and may result in overheating when only a subset of the generators is operating.

- After performing a noise study, tell the generator manufacturer the dB level that is required at 23 ft from the generator. The three typical options are 85, 75, and 65 dBa. The lower the dB, the greater the sound attenuation and the greater the cost.
- Provide the generator manufacturer with the dB requirement at the property line and the position of the generator relative to the property line. With this information, the manufacturer can do the calculations and provide the necessary attenuation.

- High harmonics: If high-harmonic content loads are connected to the generator, this may necessitate oversizing the generator.
- Leading power factor: Input filters and lightly loaded electronics can result in leading power factor loads. Leading power factor is particularly difficult for generator-voltage regulators. If leading power factor is a potential concern, identify that at the time of specification. To mitigate the issue, input filters can often be disabled/bypassed during low-load conditions.
- Elevators: Elevators may provide a significant regenerative load. Many elevator controllers can now accept a dry contact input to indicate that the elevator is “on generator.” The elevator can then be reduced to half speed to limit the regeneration on the generator.
- Altitude: Refer to the section above and make sure to apply the manufacturer-supplied derating factors.

- The most challenging starting condition for a generator is 100% block loading, so avoid this whenever possible. Break up the load into several load steps by using controls or an automatic transfer switch (ATS).
- Do not be overly conservative with voltage-dip requirements on starting. If the load can tolerate a 30% voltage dip, allow that. Specifying 20% voltage dip can result in an oversized genset.
- Start large motor loads first.
- Use variable frequency drives or reduced-voltage starting whenever possible.
- Use the “walk-in” feature of uninterruptible power supply systems that slowly transfers load from battery to generator.

- The applicable codes.
- The generator rating and fuel type.
- The environmental conditions.
- The load profile and overall loading.

- NEC, primarily Articles 445 (Generators), 517 (Health Care Facilities), and 700 (Emergency Systems.
- NFPA 99: Health Care Facilities Code.
- NFPA 110: Standard for Emergency and Standby Power Systems.

- Minimize the amount of campus real estate used.
- Assist with noise abatement. The installation is in a controlled area with tight noise restrictions. Critical generator silencers were provided on the generators and as well as noise baffling in the walls to assist with both external noise and noise transmitted internally to the medical center.

- Understand how to design ventilation systems using ASHRAE Standard 62.1: Ventilation for Acceptable Indoor Air Quality.
- Learn four strategies to realize cost and energy savings.

When designing HVAC systems to meet local codes and ASHRAE 62.1- 2016: Ventilation for Acceptable Indoor Air Quality, reducing the amount of necessary outside air that needs to be conditioned for acceptable indoor use is allowed, and there are several means by which the designer can approach such reductions, all of which are described within this ASHRAE Standard. Four strategies will be examined to save energy and realize cost savings. Approaching HVAC outdoor-air calculations in this manner may not be the easiest way to design ventilation systems, but the payoff could make it worthwhile. The potential reduction in required outdoor airflow could exceed 50% depending on what combination of strategies are implemented for a given HVAC system or a combination of systems.

D = 100/(100 + 5 x 20+50) = 0.40

Uncorrected outdoor-air intake, VV_{ou} = 0.40 x (5 cfm/person x 100 people + 5 rooms x 5 cfm/person x 20 people + 5 cfm/person x 50 people) + (0.06 cfm/sq ft x 20,000 sq ft + 5 rooms x 0.06 cfm/sq ft x 400 sq ft + 0.06 cfm/sq ft x 2,000 sq ft)
Result: V_{ou} using diversity = 1,940 cfm

VT = 3ν/V_{bz}
ν = room volume in cubic feet
v = (400 sq ft x 10 ft)
v = 4,000 ft^{3}

Occupant density = 50 people per 1,000 sq ft (from Table 6.2.2.1)
Default PDefault P_{z} = 20 people
R_{p }= 5 cfm per person (from Table 6.2.2.1)
A_{z} = 400 sq ft
R_{a} = 0.06 cfm/sq ft (from Table 6.2.2.1)

VV_{bz} = 124 cfm

T = 3ν/VT = 3 x (4,000 ft^{3})/124 cfm
Result: T = 97 minutes

This result allows the designer to take the average occupancy over a time period up to 97 minutes.
For the conference room that is occupied for only 30 minutes out of a 90-minute time period, the time-averaged zone population, Pzavg, is the average of the occupancy over that 90-minute time period.
P_{z}avg = ((20 people x 30 min) + (0 people x 60 min))/90 min
P_{z}avg = 6.667 (round to 7 people)

Thus, the outdoor airflow required is calculated with Pzavg instead of the default Pz.
V_{bz} (Time-averaged) = P_{z}avg x R_{p} + A_{z} x R_{a }
V_{bz}(Time-averaged) = 7 people x 5 cfm/person + 400 sq ft x .06 cfm/sq ft
Result: V_{bz}(Time-averaged) = 59 cfm

In this example, the required breathing-zone airflow for this conference room has been reduced by 52% from 124 cfm to 59 cfm.
For an office building that contains a large number of sparsely occupied rooms, this reduction in required, outdoor airflow can result in a significant reduction in the total required outdoor airflow that must be heated or cooled.
The two strategies noted above are not exclusive, but they can be used for the same outdoor-air calculation. Combining the results of Example 1 with Example 2, the VV_{ou} = D (R_{p}1 x P_{z}1 + 5 x R_{p}2 x P_{z}2 + R_{p}3 x P_{z}3) + (R_{a}1 x A_{z}1 + 5 x R_{a}2 x A_{z}2 + R_{p}3 x A_{z}3)
V_{ou }= 0.40 x (5 cfm/person x 100 people + 5 rooms x 5 cfm/person x 7 people + 5 cfm/person x 50 people) + (0.06 cfm/sq ft x 20,000 sq ft + 5 rooms x 0.06 cfm/sq ft x 400 sq ft + 0.06 cfm/sq ft x 2,000 sq ft)
Result: V_{ou} (time-averaging and diversity) = 1,810 cfm

VV_{bz} (high CO_{2}) = 0.06 cfm/ sq ft x 400 sq ft + 5 cfm/person x 20 people
Result: V_{bz} (high CO_{2}) = 124 cfm

VV_{bz} (low CO_{2}, reset) = 0.06 cfm/sq ft x 400 sq ft
Result: V_{bz} (low CO_{2}, reset) = 24 cfm

The values above represent two required minimum HVAC system ventilation operating conditions. The engineer must size the equipment and outdoor- and supply-air ductwork to accommodate both the high and low conditions. Due to this requirement, HVAC system capacity is not reduced, so there is no first-cost advantage to the use of DCV. In fact, DCV will generally be a higher first cost due to the additional controls complexity that is required to operate with DCV.
In example 4, the building control system can reset the outdoor airflow to this room by approximately 80% during times of normal CO- Learn how to create a circuit sizing standard.
- Know the applicable codes and standards for circuit sizing and protection.
- Understand how to develop a circuit legend that can be applied to electrical modeling software.

To efficiently, quickly, and cost-effectively design electrical systems, developing a circuit schedule that all engineers and designers can use on the project is required. With advance planning, circuit schedules can be created that handle the overwhelming majority of design conditions and ensure continuity across the design. Now that many programs are evolving from simple CAD programs to modeling programs, development of a circuit schedule can help engineers fully use their modeling capabilities. Developing the circuit standard can be broken down into a few key steps, typically completed in sequence:

- Determine the design conditions for which to build a circuit legend.
- Decide upon a naming standard.
- Determine standard circuit sizes.
- Determine standard ground sizes.
- Develop circuit legends for special conditions.

- 30°C—the default condition from NFPA 70: National Electrical Code (NEC) Table 310.15(B)(16).
- Three current-carrying conductors.
- Termination provisions of the default condition as per NEC Article 110.14(C)(1):
- 60°C for 100 amp and lower.
- 75°C for higher than 100 amp.

- Thermoplastic high heat-resistant nylon-coated (THHN) wiring (90°C).
- Copper conductors.
- A maximum conductor size of 600 kcmil. This size of conductor is widely accepted on terminations for large size breakers while 750 kcmil is less widely accepted.

- More than three current-carrying conductors in a raceway.
- Ambient temperature.
- Adjustments due to voltage drop.
- Adjusting ground conductor sizing.

- 320 amp x 0.8 = 256 amp

- 430 amp x 0.8 = 344 amp

- The sum of the noncontinuous load plus 125% of the continuous load.
- An allowable ampacity not less than the maximum load to be served after ampacity adjustment (refer to Example 3 for the application of continuous and noncontinuous loads).

- 475 amp x 0.71 = 337.3 amp

- 520 amp x 0.71 = 369.2 amp

- 600/500 = 1.2.

- 52,620 circular mils x 1.2 = 63,144 circular mils

- Determine the overcurrent protection required.
- Choose the circuit that matches the OCPD.
- Verify that the calculated ampacity of the circuit is greater than or equal to the required ampacity.

- Check the terminations. Per NEC 210.19(A)(1)(a), the ampacity of the circuit must be 125% of the continuous load.
- 23 amp x 1.25 = 28.8 amp.
- The ampacity of our conductor using 60°C terminations is 30 amp, so our circuit is acceptable.
- Per NEC 210.19(A)(1)(b), the adjusted ampacity of the circuit must be greater than the load we are serving. Our load is 23 amp and, per Table 7, the adjusted ampacity is 32 amp, therefore circuit 30CU-3N is acceptable.

- Check the terminations. Per NEC 210.19(A)(1)(a), the ampacity of the circuit must be 125% of the continuous load.
- 286 amp x 1.25 = 357.5 amp.
- The ampacity of our conductor at 75°C must be greater than 357.5 amp. In this case, our circuit ampacity is 525 amp, so our circuit is acceptable.
- Per NEC 210.19(A)(1)(b), the adjusted ampacity of the circuit must be greater than the load we are serving. In this case, our adjusted circuit ampacity is 369.2 amp and our load is 286 amp, thus our circuit is acceptable.

- Check the terminations. Per NEC 215.2(A)(1)(a), the ampacity of the circuit must be 125% of the continuous load.
- 1.25 x (286 amp + 310 amp + 23 amp) = 773.8 amp.
- The ampacity of our conductor at 75°C must be greater than 773.8 amp. In this case, our termination ampacity is 840 amp, so our circuit is acceptable.
- Per NEC 215.2(A)(1)(b), the adjusted ampacity of the circuit must be greater than the load we are serving. In this case, our adjusted circuit ampacity is from Table 7 is 760 amp and our load is 286 amp + 310 amp + 23 amp = 619 amp, therefore our circuit is acceptable.