Do Train-the-Trainer Programs Work?

2013 has been an exciting year!  I have conducted more than 30 training classes on electrical safety, including topics such as basic electrical safety, shock and arc flash hazards, coordination of protective devices, control of hazardous energy (LOTO), and the design of equipment and machines.  These classes reference material from OSHA 29 CFR 1910, NFPA 70, NFPA 70E, NFPA 70B, NFPA 79, many UL and IEC standards.  Class participants range from people that were on the job for less than 3 months to people with more than 30 years of experience.

A couple of times a year I get asked if I could conduct a train-the-trainer program.  Before you decide on whether or not to have a train-the-trainer program, let’s look at the reasons behind using internal resources to train employees and what these trainers need to know and have available.

There are many good reasons to have in-house experts who can provide training to increase the knowledge and productivity to an organization’s most important resource (their people).  Here are a few:

• Reduce the cost of training
• Flexibility when and where to offer training
• Allow for the development of internal experts
• Provide career advancement of internal experts

Unlike K-12 teachers, college professors and professional trainers or instructors have little formal training in teach methodologies, and no licensing requirements.  People can obtain professional certifications that can demonstrate some level of competency, e.g. PMP, NCE, CPP, PE, MBA, PhD, etc.  Trainers can also follow specific training guidelines from organizations such as the American Institute of Architects (AIA) for conducting professional training.  However, following specific training guidelines or having a certification in a topic does not necessarily make you a good trainer or instructor.  In fact, many can recall college courses or professional training programs that were really good and others that were less than desirable.

To be a good professional trainer or instructor, you need to have the following:

• Expertise (experience and training) in the field
• Expertise (experience and training) in teaching methods
• Ability to speak in front of groups of people, both large and small
• Ability to connect with people from all functional areas of an organization
• The resources (time and finances) to adequately prepare to teach classes
• Passion for the topic(s)

Experience and knowledge of the topic and how to conduct a training class are essential to teach others.  Without knowing how to put together a training program, devising practical examples, or understanding how to evaluate participants, the training programs will not deliver the anticipated results.  It is also important that the trainer have sufficient resources available.  These resources include not only the time to prepare for the programs they teach, but also the resources to have adequate support materials to augment the learning processes.  For someone teaching electrical safety, this includes personal protective equipment (PPE), voltage rated tools, and other items to ensure that participants can practice working safely in a safe environment.

The final ingredient for a trainer or instructor is passion for the topic.  If a person is passionate about the topic, they will be able to overcome any obstacle in their way.

If you are looking for an internal person to be the professional trainer or instructor, please make sure you have identified a person who has the experience, the training, the personal style, the resources (time and finances) and the passion to teach the topic.  If any of these are missing, then your money is better spent using a resource outside of your organization as the train-the-trainer program is probably not going to work.

Calculating Short Circuit Currents (SCC)

In my last blog post (which was much too long ago), I wrote that the National Electric Code (NEC) requires the equipment be “selected and coordinated to permit the circuit protective devices used to clear a fault to do so without excessive damage to the electrical equipment of the circuit” [1].  To achieve a safe condition requires that equipment connected to the electrical system have short circuit current rating (SCCR).

To ensure that the equipment is being installed such that the calculated or tested SCCR is sufficient, a short circuit current (fault current) study must be performed.  Short circuit current (SCC) studies can be conducted through hand calculations, or software simulations.  Software simulations are the main method for conducting short circuit current studies.  While there are a number of vendors of this software, EasyPower, SKM, and ETAP seem to be the most used.

To aid engineers or installers when an SCC is not readily available, one can approximate the SCC to determine whether or not the SCCR of the equipment is suitable for the point of application.  The approximation of the SCC can be conducted by referencing the parameters of the closest upstream transformer and conducting some simplistic calculations.

The SCC calculation at the secondary of the transformer can be determined by the power rating of the transformer (P), the full-load secondary current of the transformer (I), the line-line voltage at the secondary of the transformer (V) and the transformer impedance (Z) [2].  The power rating is in kVA, the current is in amperes (A), the voltage is in volts (V), and the transformer impedance is in percent.

The full-load secondary current (I) of the transformer can be calculated by EQ1.

                                                     I = P / (V * SQRT(3))       EQ1

The SCC can be calculated by EQ2

                                                           SCC = I / Z    EQ2

 

As an example, suppose that we were going to install an industrial control panel on circuit that was supplied from a 500 kVA transformer with a voltage of 480 V, 3W+G, and an impedance of 3 %.  Using EQ1 and EQ2 yields a short circuit current of 20.05 kA.  To properly apply the industrial control panel, the equipment is required to have an SCCR that is greater than 20.05 kA. 

 

Common values of equipment SCCR are 5 kA, 10 kA, 14 kA, 22 kA, 25 kA, 30 kA, 42 kA, 50 kA, 65 kA, 85 kA, 100 kA, 125 kA, 150 kA, and 200 kA [3].   

 

An industrial control panel for this application would need to have an SCCR of at least 25 kA.  The SCCR can be calculated using UL508A Supplement SB.

 

This is a simplistic calculation that does not take into account the parameters associated with electrical conductors.  Also, as the power rating (P) of the transformer increases, the available SCC increases.  As the impedance (Z) transformer increases, the available SCC decreases.

Ensuring the equipment is properly applied is the responsibility of engineers and installers.  The NEC requires that equipment have an SCCR that is equal to or greater than the SCC at the point of installation.  Appling an industrial control panel or any other electrical equipment with an SCCR that is less the SCC at the point of installation will compromise the safety of nearby personnel.

REFERNCES.

1. National Fire Protection Association (NFPA).  National Electric Code, NFPA 70-2011, Quincy, MA USA
2. McKeown, D., Simple Methods for Calculating Short Circuit Current without a Computer, Retrieved 2012 August 10, Available [on-line] at http://www.geindustrial.com/publibrary/checkout/Short%20Circuit?TNR=White%20Papers|Short%20Circuit|generic.
3. Underwriters Laboratories (UL).  Standard for Safety Industrial Control Panels, UL 508A, Northbrook, IL USA

What is SCCR and Why is it Needed

From an electrical safety perspective, the past couple of months have been interesting.  Whether from recent posts of properly applying Industrial Machines or Industrial Control Cabinets, the number of electrical safety training programs that I have taught, or the meetings and phone calls, there are questions around short circuit currents, fault-currents, short circuit current ratings (SCCR) and why they are important.

Short circuit current and fault current are often used interchangeably.  However, there are some differences.  A short circuit current is an abnormal condition where two or more conductors of opposite polarity (or ground) are connected together and where the only limiting impedance is that associated with the resistive and inductive parameters associated with the electrical system [1].  Fault current is any abnormal current that flows in an electrical circuit [2].  Fault current can be from an unintended short circuit, transient current, overload current, or other abnormal condition.

Short circuit current rating (SCCR) refers only to equipment or systems and is a parameter associated with the connection to the electrical system.  SCCR is defined as “The prospective symmetrical fault current at a nominal voltage to which an apparatus or system is able to be connected without sustaining damage exceeding defined acceptable criteria” [3]. 

When installing electrical equipment or systems (including machines), the National Electric Code requires that equipment be “selected and coordinated to permit the circuit protective devices used to clear a fault to do so without excessive damage to the electrical equipment of the circuit” [3].  Equipment that is Listed and applied within their Listing requirements are properly applied [3].

Depending on the equipment or machine, SCCRs can be determined through testing or through calculations.  Switchboards, switchgear, panelboards, transfer switch equipment, surge protective devices (SPDs) and the like require testing to obtain their SCCR.  The SCCR for industrial machines and industrial control cabinets can be calculated using Underwriter Laboratories Standard for Safety, Industrial Control Panels, UL 508A; although these calculations are a result of known practices from tested results.

Listing agencies (like UL, ETL, TUV, etc.) that conduct testing to determine the SCCR of equipment are doing so to determine if the equipment is “safe” for installation and operation at the SCCR.  Within product safety standards, Listing agencies have predetermined pass/fail criteria.  While the pass/fail criteria vary slightly standard to standard, common examples include [4]:

• Emission of flame, molten metal, glowing or flaming particles through any openings (preexisting or created as a result of the test) in the product.
• Charring, glowing, or flaming of the supporting surface, tissue paper, or cheesecloth.
• Ignition of the enclosure
• Creation of any openings in the enclosure that result in accessibility of live parts, when evaluated in accordance with the accessibility of live parts
• Loss of structural integrity to a degree that the equipment collapses or experiences such displacement of parts that there is a risk of short-circuiting or grounding of current-carrying parts.
• Opening of an external leads or conductors.

To ensure that the equipment or machine is installed in a manner that reduces electrical hazards, the device must have a short circuit current rating (SCCR) that is equal to or greater than the short circuit current at the point of installation.  Equipment that has a SCCR less than the short circuit current at the point of installation increases the probability of electrical hazards (both Shock and Arcing Hazards), is inconsistent with standards, and can result in injuries to employees or personnel.

Part of engineering equipment or a system includes not only ensuring that it functions properly, but also ensuring that it is installed in a manner that does not create hazardous conditions.  Knowing what the short circuit current at the point of installation and the SCCR of the equipment is one step in determining if the equipment is properly applied.

 

1. Wikipedia.  Short Circuit Current.  Retrieved 2013 March 23.  Available [on-line] at http://en.wikipedia.org/wiki/Short_circuit
2. Wikipedia.  Fault Current.  Retrieved 2013 March 23.  Available [on-line] at http://en.wikipedia.org/wiki/Fault_(power_engineering)
3. National Fire Protection Association (NFPA), National Electric Code, NFPA 70-2011, Quincy, MA USA
4. Underwriters Laboratories (UL), Standard for Safety, Surge Protective Devices, UL 1449 3^rd edition, Northbrook, IL USA

 

Installation of Industrial Control Panels

This month, the topic is the Installation of Industrial Control Panels.

An industrial control panel is an assembly of two or more components consisting of one of the following:

1. Power circuits components only; e.g. motor controllers, overload relays, fused disconnect switches, and circuit breakers
2. Control circuit components only, e.g. pushbuttons, pilot lights, selector switches, timers, switches, control relays
3. A combination of power circuit and control circuits [NFPA 70-2011]

Industrial control panels do include the controlled equipment, but does include all terminations, wiring, enclosures, and other ancillary devices required to connect the components [NFPA 70-2011].

The minimum installation requirements for an industrial control panel is that it meets the requirements detailed in the National Fire Protection Association (NFPA), National Electric Code, NFPA 70-2011, Article 409, Industrial Control Panels.  There are two types of requirements within NFPA 70-2011, Article 409: Installation (marking), and Construction requirements. 

An industrial control panel is required to have a label on the enclosure with the following information:

1. Manufacturer’s name, trademark, or other descriptive marking
2. Supply voltage, number of phases, frequency, and full-load current for each incoming supply
3. Short-circuit current rating (SCCR) of the industrial control panel using an approved method, unless the industrial control panel only contains control circuit components
4. Electrical diagram number(s) or the number of the index to the electrical diagrams
5. Enclosure type
6. If the industrial control panel is intended for a service entrance application, it shall be marked accordingly
7. Industrial control cabinets supplied by more than one power source shall be marked

Industrial control panels are also required to have specific components within the industrial control panel analyzed for proper and safe operation.  This includes:

1. Overcurrent protection (internal or external)
2. Equipotential bonding of all grounded parts
3. Proper wiring space and wiring utilization
4. Proper spacings between adjacent components
5. Proper disconnecting means for all motor loads

Industrial control panels for use in the US are not required to be Listed or Approved by an OSHA Nationally Recognized Testing Laboratory (NRTL), but it is a good idea.  As the reader will note, there are minimal operational or product safety requirements defined in the NFPA 70-2011, Article 409.  From a product safety standpoint, NFPA 70-2011, Article 409 does not have requirements regarding leakage current, that the internal components are used in accordance with their operating limitations, or that the industrial control equipment does not create a safety hazard when exposed to normal or abnormal operating conditions.

Evaluation of an industrial control panel to product safety standards will reduce the potential of the equipment presenting a product safety hazard.  The most notable safety standard for an industrial control panel in the US is Underwriters Laboratories (UL), Standard for Industrial Control Panels, UL 508A.  However, UL 508A is in a transition phase where it will soon be obsolete.  To harmonize with international standards, UL will be moving to the UL, Low-Voltage Switchgear and Controlgear, UL 60947 series of standards.  There will be a number of standards for specific components used for industrial control panel and auxiliary equipment applications. 

After 2012 January, all industrial control panels will be evaluated to UL 60947 unless the manufacturer request’s the industrial control panel be evaluated to UL 508A.  After 2017 January, all industrial control panels must be evaluated to UL 60947 to maintain Listing or Approval.

To ensure the best installation of an industrial control panel, the equipment should be Listed or Approved to UL 508A or UL 60947 by an NRTL and installed in accordance with the requirements of NFPA 70-2011, Article 409.  In addition, a Risk Assessment should be conducted to ensure that operational and safety requirements not identified in the standards have been accounted for.

For more information, please contact me by commenting on this blog or sending me an e-mail.

 

Installation of Industrial Machines

As I noted in my 2012 December blog, for 2013 I intend to focus more on installation issues.  The first topic for 2013 is on Industrial Machines.

Industrial machines are defined as a power-driven machine that is used to process material by cutting; forming; pressure; electrical, thermal, or optical techniques; lamination; or a combination of these processes, and can include associated equipment used to transfer material or tooling, including fixtures, to assemble/disassemble, to inspect or test, or to package [NFPA 79-2012].  Industrial Machines come in many different sizes, shapes, operating characteristics and incorporate a variety of components including power, control, monitoring, signaling, heating, movement and measurement.  Industrial Machines encompass a large category of equipment, but they do not include hand-held or portable devices.

For equipment that is installed in the US, the manufacturer should have their Industrial Machines evaluated to Electrical Standard for Industrial Machinery [NFPA 79].  If the Industrial Machine is intended for use outside of the US, many countries have adopted Safety of machinery – Electrical Equipment of Machines – Part 1: General Requirements [IEC 60204-1] as the standard used to evaluated Industrial Machines. 

While evaluation to consensus standards such as Electrical Standard for Industrial Machinery [NFPA-79] is not mandatory in the US, installers are required to meet the minimum requirements detailed with the National Electric Code [NFPA 70].

The National Electric Code has three main requirements for Industrial Machinery.  The first requirement is that the Industrial Machine be provided with a permanent nameplate.  The nameplate shall have the following information:

1. Supply voltage, number of phases, frequency, and full-load current
2. Maximum ampere rating of the short-circuit and ground-fault protective device
3. Ampere rating of largest motor
4. Short-circuit current rating (SCCR) of the machine industrial control panel
5. Electrical diagram number(s) or the number of the index to the electrical diagrams

The second requirement addresses the requirements for the supply conductors and the overcurrent protective device.  These requirements are:

1. The supply conductor shall have an ampacity that is the sum of:
1. 125 percent of all resistive heating loads
2. 125 percent of the highest rated motor load
3. 100 percent of all connected loads
2. The Industrial Machine shall have a disconnecting means
3. The Industrial Machine shall have overcurrent protection, whether contained integral or external to the device

The third requirement is that the Industrial Machine shall not be installed where the available fault current exceeds the short-circuit current rating as marked on the nameplate of the Industrial Machine.

Installing an Industrial Machine to the requirements of the National Electric Code [NFPA 70] will limit the potential for overcurrent conditions to damage the facility.  To provide personnel protection from normal and abnormal operating conditions of the Industrial Machine, Electrical Standard for Industrial Machinery [NFPA-79] provides more comprehensive requirements.  Some of the requirements include:

• Disconnect and overcurrent protection
• Grounding and bonding
• Power system interactions
• Internal and external conductor sizes, colors, and routing
• Control system performance and safety
• Enclosure types, openings, spacings, and guarding
• Labeling and documentation

For more information, please contact me by commenting on this blog or sending me an e-mail.