Each of our electrical power system studies or electrical engineering design services were developed to proactively evaluate our client’s electrical power system’s needs and effectiveness, to pinpoint and correct potential issues quickly, identify utility and construction cost saving opportunities, and without costly interruptions to the electrical service.
We can assist to: minimize down time and power outages, identify potentially faulty and dangerous equipment, develop strategic predictive/preventative maintenance and trouble-shooting programs, verify compliance to the electrical code and insurance company requirements.
Electrical Distribution System Analysis and Testing Services
SAMPLE: Short Circuit Studies, Single Point of Failure Analysis
What are Short Circuit Currents?
Short-Circuit Currents are currents that introduce large amounts of destructive energy in the forms of heat and magnetic force into a power system, as indicated by IEEE 242-1986, IEEE Recommended Practice for Protection and Coordination of Industrial and Commercial Power Systems ( Buff Book).
Risks Associated With Short Circuit Currents?
The building/facility may not be properly protected against short-circuit currents. These currents can damage or deteriorate equipment. Improperly protected short-circuit currents can injure or kill maintenance personnel. Recently, new initiatives have been taken to require facilities to properly identify these dangerous points within the power distribution of the facility.
Why obtain Short Circuit Studies and its Advantages.
Short circuit studies (Fault Current) are required to insure that existing and new equipment ratings are adequate to withstand the available short circuit energy available at each point in the electrical power distribution system. Fault currents that exceed equipment ratings are capable of extensive equipment damage and are a serious threat to human life.
On large systems, short circuit studies are required to determine both the switchgear ratings and the relay settings. No substation equipment, motor control centers, breaker panels, etc. can be purchased without knowledge of the complete short circuit values for the entire electrical power distribution system.
The short circuit calculations must be maintained and periodically updated to protect the equipment and the lives. It is not necessarily safe to assume that new equipment is properly rated.
Typical Analysis Report Includes: Short circuit calculations, which highlights any equipment that is ascertained to be underrated as specified; suggested modifications to rectify the underrated equipment; (trip sizes within the same frame, the time curve characteristics of induction relays, CT ranges, etc.). The Protective Device Setting and Coordination Studies are the suggested follow on analysis to develop the coordination curves, highlighting areas lacking coordination. Present a technical evaluation with a discussion of the logical compromises for best coordination.
Protective Device Coordination studies are required to ensure the safety including personnel and general public and to ensure that equipment is not damaged under fault conditions per the requirements of NEC 110-10. Analysis of Time Current Characteristics (TCC) data for the protective devices and equipment (such as transformers and cable) is used to permit the circuit-protective devices to clear a fault without extensive damage to the electrical components of the circuit.
There is a second type of coordination, known as Selective Coordination which uses the TCC curves to ensure that faults (short circuits) affect the least possible portion of the electrical distribution system. Improper selective coordination or no selective coordination can result in faults on branch circuits shutting down complete operations for parts or possibly a whole building, manufacturing facilities. Such undesirable events result in loss of production, loss of business income, inconvenience to customers and risk of injury. These losses can be minimized or completely eliminated by proper Selective Coordination, the second benefit of performing coordination studies.
Correct setting values can only be determined by a study based on all the pertinent electrical characteristics of the equipment in the system.
The “Power Quality Analysis” evaluates the electrical energy going to equipment in the form that will allow the system to operate properly, efficiently and minimize long term risk to that equipment. The parameters of Power Quality include voltage, frequency and waveshape most generally in the form of a sine wave. Most computer equipment will operate within a certain tolerance curves. This study will verify if specific equipment tolerances, as specified by the manufacturer, and verify if the power quality is adequate for the equipment to run properly.
Troubleshooting power quality problems can be accomplished in many ways. One of the simplest methods is to start off by determining into which of four major categories a potential problem falls. These areas are 1) A grounding problem, 2) A transient problem, 3) A harmonics problem or 4) No power quality problem at all. Each of these studies, are listed within.
We can diagnose any of these problems to help you control and monitor these events. We can also design and install a permanent system that will send all of the data to a central computer within the facility. We can then provide consultation services when future problems arise.
Suggested Services for the Study:
Power Quality Monitoring and On Site Measurements:
Harmonic Analysis Studies are required to insure that problems will not be introduced into the electrical distribution system due to non-linear loads. Loads which draw a non-sinusoidal current when a sinusoidal voltage is applied is defined as non-linear. The increased use of electronic power devices, which chop or abruptly switch power, introduces harmonics to the power system.
Harmonic currents can increase the heating of conductors and transformers to detrimental levels, as well as causing performance interference with some load devices. IEEE Standard 519 defines the characteristics of the harmonic distortion that is allowed at the interface point with the utility. A Harmonic Analysis Study will indicate if the power distribution system is in compliance with IEEE Standard 519.
Harmonic Analysis Studies are a prime aid in designing and implementing corrective filter systems for harmonic effect minimization. Study considerations include harmonic effects from power factor correction capacitors, resonance cond
Suggested Services for the Study
Earthing / Grounding defines the electrical potential of the conductors relative to the Earth’s conductive surface. Grounding of electrical equipment serves several purposes.
The first reason is to ensure safety from over voltages, faults and lightning. If a fault within an electrical device connects an ungrounded supply conductor to an exposed conductive surface, anyone touching it while electrically connected to the earth will complete a circuit back to the ungrounded supply conductor and receive an electric shock.
And, Grounding provides stability of system voltages by providing a solid reference to earth and establishing a reference to control electrical “noise” that might interfere with the proper operation of electronic equipment.
Ground faults can destroy human life and the facilities electrical equipment, in seconds. A well designed ground fault protection system will minimize damage, due to a ground fault, to acceptable levels.
We can assist our clients to find out more about any of these topics affect your building and how we can assist to: Improve safety of the workers, reduce damage and maintain process continuity during a ground fault, decrease voltage transients and limit damage due to arcing ground faults, understand what is adequate protection required, how and where neutrals should be bonded, adequate current sensor installation, causes of failure trips or lack of trip of the protective device, voltage drop, fault currents, fuse or circuit breaker protection, high impedance line-to-ground faults, over current protection, residual-current device, ground fault circuit interrupters, surge suppressors, electromagnetic interference filters, antennas and measurement instruments and update the standards to meet NEC code.
The Load Flow and Voltage Drop study is the most basic and commonly needed electrical study.
Load Flow Study – Show the power in kVA or Amperes that is being handled by all of the individual electrical components, e.g. transformers, conductors and panels in the system. This allows a determination of equipment rating margins and reserve capacity loading percentage.
Voltage Drop Calculations – for each bus and at all equipment will indicate if equipment supply voltages are at levels which will adversely affect equipment life or performance.
Loads can be modeled as any combination of constant kVA, constant current and constant impedance. The study will take into account tap positions on transformers and indicate where tap changes should be made. Load Flow / Voltage Drop studies may cover conventional voltage drop analysis, loss analysis, power factor considerations, capacitor placement, long line charging effects, impact loading for motor starting and co-generation analysis. A base-line Load Flow / Voltage Drop study should be performed anytime major changes are made to the power distribution system.
Suggested Services for the Study:
Starting large motors can cause disturbances to the motor and other loads on other buses. In the worst cases the starting motor may stall and be unable to start the driven load. In general, a motor starting study should be made if the motor’s horsepower exceeds approximately 30% of the supply transformers base kVA rating. If the generator supplies the motor, use 10 -15% of the generator kVA rating.
Motor starting studies can vary from basic voltage drop on the system to a detailed waveform presentation of motor bus voltage, motor speed and motor torque, acceleration torque, load torque, power factor, rotor and stator currents, motor slip, real, reactive and total power.
One of the most common side effects of starting large motors is a serious voltage dip on the buses throughout the facility. This voltage dip will cause other motors to slow down. In severe cases other motors may reach the stall point causing a domino effect to the voltage drop. Control relays may not hold and auxiliary equipment may be affected. In addition to these secondary effects the life of all motors on the system may be shortened. Ideally a transient motor starting study should be preformed which shows a time/voltage waveform for the motor bus. Motor starting studies should be performed prior to the ordering of large motors, such that the motor can be installed with confidence that the motor’s life and applications performance will be satisfactory and the remainder of the power distribution system will not be adversely affected.
Dynamic Simulation Studies for Transient Conditions are required to insure that the electrical distribution system will remain stable or quickly recover from disturbances including faults switching, load changes, motor starting, loss of generation, loss of excitation and blocked governors.
Parameters which are analyzed include – absolute or relative machine angle, machine speed, machine mechanical power, machine electrical power, machine terminal voltage, exciter field voltage, bus frequency, branch power flow (real and reactive), branch current, branch apparent resistance and reactance.
The goal of every infrared electrical test is to scan designated electrical equipment, to pinpoint defective components and elevated temperatures within your power distribution system. If unfound or treated these “hot spots” can cause- potential fire, explosion, or service interruption threats.
Hot spots are typically caused by unbalanced or overloaded electrical circuits, loose connections, or broken equipment. These conditions are often overlooked during routine evaluations of facilities and can result in the release of heat that will be visible through an infrared camera.
We will utilize an infrared camera to evaluate our client’s system and provide a well organized, easy to read and detailed report with results of the test including: information on testing procedure, all data and statistical calculations, identified problem hot spot locations and provide recommendations to take corrective action.