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System Modeling

The basis for any electrical system analysis is the construction of an appropriate model of the system under study. Such a model includes all of the system parameters that are relevant to the analysis to be performed. The model then forms the foundation upon which the analysis is built.

JanCom Technologies, Inc. begins any system analysis with the collection of all pertinent data. A computerized model is then developed utilizing such software as Microsoft Excel, AutoCAD, EDSA, and/or others, as appropriate for the analysis to be performed.

Fault (Short Circuit) Current Analysis

The National Electrical Code and safe design practices dictate that the components in an electrical distribution system be capable of interrupting or withstanding, as appropriate for the type of component in question, the current that would be available at its location in the circuit during a worst-case fault, or short circuit, condition. Devices, such as circuit breakers, that are not adequately rated for the available fault current may catastrophically destruct when subjected to the extreme magnetic forces associated with a fault condition. This may result in damage to the equipment in which the devices are installed or injury to personnel who may be nearby. The amount of fault current available at each point in the distribution system if the fault were to occur at that location is a function of how much fault current the electric utility can supply, based on the characteristics of the utility provider's transmission and distribution system, and the impedance present in the system between the service point and the location in question. The values of the available fault current at each point in the system are determined by mathematically modeling the distribution system and calculating the currents.

JanCom Technologies, Inc. uses state-of-the-art software to model the distribution system and perform the required calculations. Once the fault current values are determined, they are compared with the interrupting or withstand ratings for the equipment installed or proposed for installation to determine whether it is being applied within it's fault current ratings. Deficiencies are then identified for correction.

It is recommended that such a fault study be performed prior to the construction of a new facility and for an existing facility for which the electrical service capacity has been upgraded or which has undergone major distribution system changes.

Protective Device Coordination Studies

When an adverse condition, such as an equipment failure, creates an overload condition in some portion of a distribution system, it is highly desirable to have the nearest upstream overcurrent protective device -- circuit breaker or fuse -- open and clear the overload condition. If a protective device further upstream opens, the result is that electrical service is removed to more of the loads than necessary. In extreme circumstances, the main breaker or fuses for a facility may open, resulting in a total "blackout" condition. Properly selecting the specific overcurrent protective devices or the settings of adjustable protective devices so that only the device nearest the overload opens yields a "coordinated" system. While total, perfect coordination among all the protective devices in a distribution system is rarely attainable due to limitations in the trip characteristics of typical devices, a carefully performed Coordination Study, followed up by the implementation of the results of the study, can maximize the coordination to the greatest extent practical.

In the performance of a Coordination Study, each path in the distribution system is isolated and the trip characteristics of the devices in the path are compared. This is most commonly done graphically, with trip time and current forming the axes of the graphs and the trip characteristics of the devices represented as curves on the graphs. The goal is to eliminate overlap between the curves of the devices.

JanCom Technologies, Inc. utilizes modern software to perform the graphical analysis and comparison of the trip characteristics of the devices proposed for a new system or installed in an existing system. Where overlap occurs, the use of devices with different trip characteristics or different settings of adjustable devices may be recommended.

Other Systems Analysis Capabilities

JanCom Technologies, Inc. also offers a wide range of other electrical systems analysis services. These include the performance of Power Factor Studies with the design of corrective measures, Harmonics Analyses, Power Quality Studies, and RAM (Reliability/Availability/Maintainability) Studies.
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