ELECTRICAL STUDIES

In order to comply with the NOM-029-STPS-2005, the quality indicates in its paragraph 5.2 that it must “have the unifilar diagram of the electrical installation of the work center updated and with the table of general loads of loads. .. “ The single-line diagram is a simple, comprehensive graphic representation of the electrical system, showing the substations, transformers, boards, feeder and derivative circuits, as well as the interconnection between them. A Single Line Diagram is composed of all the electrical control equipment and / or force installed on the premises, as well as characteristics of conductors, electrical protections and other equipment that make up the electrical installation, for example, a single line diagram will contain information from its substation (if any) to the last contact in their offices, of course, based on the ranges required, ie any single line diagram can develop as specific as necessary.

The vast majority of problems and breakdowns in the industrial environment – whether mechanical, electrical or manufacturing – are preceded by temperature changes that can be detected by temperature monitoring with Infrared Thermal Vision system. The complementation of thermographic inspection programs such as predictive maintenance in installations, machinery, electrical panels, etc. is possible to limit the risk of equipment failure and its consequences, while also offering a tool for quality control of repairs made. With the use of thermography the following advantages are obtained: Method of analysis without stopping production processes, saves costs. Low danger for the operator by avoiding the need for contact with the equipment. Exact determination of deficient points in a process line. Reduce repair time by accurately locating the Fault. Provides very accurate reports to maintenance personnel. Helps follow up on previous repairs. Protection against inconveniences caused by the unexpected failure of an element, by detecting it before it occurs. When a connection is loose or has some type of corrosion, its resistance increases and given that the resistance also increases the drop of tension and generates an increase of the heat, we can detect a failure before it produces a breakdown by means of a thermographic camera. An imbalance can be due to several reasons: a power supply problem, low voltage in one phase or a break in the insulation resistance of the motor coils. This causes motors and other loads to require more current, to have a lower torque (with the associated mechanical stress) and to break down sooner. Thermal imaging of electric motors operates in their operating conditions through surface temperature. Ideally, motors should be checked when working under normal operating conditions. Unlike infrared thermometers that can only capture temperatures at a single point, a thermographic camera can simultaneously capture point mileage temperatures of all major components: the motor, the shaft coupling, the motor and shaft bearings, and the control box/connections. Most motors are equipped to operate at a temperature never exceeding 40ºC. In general, an increase of 10°C above the specified temperature reduces the service life of the engine by half.

A short circuit is an electrical phenomenon that occurs when two points between which there is a potential difference can be established in contact with each other, characterized by high circulating currents up to the point of failure. It can be said that a short circuit is also the establishment of a very high electric current flow, due to a connection by a low impedance circuit, which frequently always occurs by accident. The magnitude of the short-circuit current is much greater than the nominal or charge current flowing through it. Even in installations with the most sophisticated protections, short-circuit faults occur. A high short-circuit level and a poor selection of interrupting capacities of the equipment can lead to a scan and even fire in the event of a short-circuit fault. The short-circuit analysis serves to verify compliance with ART 110-9 of NOM-001-SEDE, which states that: “equipment controlled to interrupt the passage of electrical current in the event of a fault must have a range of operation sufficient for the nominal electrical voltage to interrupt the available current.

he objectives of an electrical protection and coordination system are to prevent injury to personnel, reduce damage to system components, and limit the extent and duration of service interruption when equipment failure, human error, or adverse natural conditions occur anywhere in the system. The circumstances that cause system malfunction are usually unpredictable, based on an excellent design and a preventive maintenance program can reduce the failures that happen. The electrical system must be designed and maintained so that it is automatically protected. Preventing human injury is the most important goal of an electrical protection system. Short-circuit analysis is the starting point for the study of protection coordination. This study is based on the short-circuit calculation memory, in addition to the nominal characteristics of all the equipment and devices selected in this network. The methodology for the overcurrent protection coordination study consists of determining the operating points of the protection device curves and the time-current characteristic curves of the system series elements, which are expressed in logarithmic axes, to give as a result the final coordination graph. The protection device close to a specific load must operate quickly, according to the established times, operating with a certain time delay the next protection that is towards the source. Input current or energization of transformers Damage curves of cables and transformers Starter profile of the motors Static or resistive loads, etc.

The SE’s Arc Flash evaluation helps determine required safety limit distances and arc hazards, preventing injury or death to operating and electrical maintenance personnel. This information specifies the personal protective equipment required as well as warning labels for safe work on devices, which are placed on the doors of the cubicles of the boards. The program (SKM Power Tools) calculates incident energy according to NFPA70E, OSHA (Occupational Safety and Health Administration) and IEEE 1584 standards. The calculation of the electric arc is based on the electric arc program (electric arc) which interacts with: 1) the electrical failure levels of the short-circuit study. 2) the proposed adjustments in the protection devices previously developed in the protection coordination study. And as a result the program determines the distances to reduce the risk of burns as follows: Electric arc distance. Safe working distance. Restricted working distance. Prohibited working distance. Class of clothing required (personal protective equipment). The labels required by the Electric Arc study to be printed and installed by the customer are provided with the following questions about the following legend: Electric arc risk, electric shock hazard, work safety distance: approach limit, arcing protection limit, restricted approach, prohibited approach, type of shirt and pants, type of personal protective eyewear required for each board in compliance with NFPA 70-2004 (NEC) section 110.16. For calculation, consider the databases of short-circuit and protection coordination studies. Reference is also made to the Schematic One-Wire Diagram. In the present study, reference is made to the protection devices and buses of the schematic one-line diagram.

In alternating current circuits, the current absorbed by a load may be represented by two components: – The active IR component, in phase with the supply voltage, which is directly related to the useful work carried out (and, therefore, with the proportional part of energy transformed into energy of another type: mechanical, luminous, thermal …); – The reactive IQ component, perpendicular to the voltage, which serves to produce the flux necessary for the conversion of powers through the electric or magnetic field and is an index of the energy exchange between the supply and the element of the electrical installation. Without this component there could be no net transfer of power, for example, by magnetic coupling intervention in the core of a transformer or in the air gap of a motor.
Generally, in the presence of ohmic-inductive loads, the total current is out of phase and delayed with respect to the active IR component.
Therefore, in an electrical installation it is necessary to generate and transport, in addition to the useful active power P, a certain reactive power Q, indispensable for the conversion of electrical energy that is not controlled by the element but exchanged with the network. The complex of the power generated and transported constitutes the apparent power S. The power factor is defined as the relationship between the active component I R and the total value of current I, being the phase angle between voltage and current. With a given voltage V of the resulting phase:

Correcting’ means acting to increase the power factor in a specific section of the installation, locally the reactive power necessary to reduce, with equal power required, the value of the current and, therefore, of the power passing through the red waters above. When applying the correction in an installation, select locally the necessary reactive power, reduce the value of the current, and therefore the overall power consumed upstream. This brings additional advantages, among them, an optimized use of machines (generators and transformers) and power lines (transmission and distribution). With all this, the main advantages of correction can be summarized as follows:
optimised use of electrical machines; optimized use of power lines;
reduction of losses;
reduction of voltage drop.

Studies to assess the quality of electrical energy by identifying electrical disturbances such as overvoltages, harmonics, high frequency noise, transient voltages, wave distortions, interruptions, frequency variations, etc. Voltage, current, frequency, active power, reactive power and power factor are also measured.
We have the latest generation calibrated equipment, at the end of the study a report is delivered with the results obtained and the conclusions, the areas of opportunity detected are identified and the way to correct them is indicated.
We also offer supply and installation of the necessary equipment to correct detected deviations such as harmonic filters, capacitor banks, voltage suppressors, etc.
Power quality studies are increasingly necessary due to the more frequent presence of electronic equipment and devices that are much more sensitive to electrical disturbances. Power quality studies allow us to take the necessary actions on the electrical installation in order to avoid equipment damage and suspension of activities.
The disturbances detected in power quality studies come from both the power grid and the inside of the facility that are generated by the equipment itself. Among the main disturbances detected in power quality studies are: voltage interruptions and drops, harmonics and interharmonics, temporary overvoltages, overvoltages, transient overvoltages, voltage fluctuations, voltage imbalances, frequency variations, etc.
Power quality studies have shown that the effects of electrical disturbances can be immediate causing a machine to stop or malfunction and can also be medium or long term due to the premature aging of equipment that is produced by heating and electrodynamic stresses that occur with electrical disturbances.
The importance of power quality studies lies in that they allow us to detect disturbances and once identified we can establish equipment to counteract them as harmonic filters, regulators, capacitor banks, and so on.
Power quality studies detect deviations in the appropriate voltage, current or frequency conditions that can cause failures such as: overheating of equipment, low power factor, failures in control devices, damage to control cards and failures in computer systems and PLC´s among others.