power systems loss

IEEE GUIDE FOR FIELD TESTING OF RELAYING CURRENT TRANSFORMER C57.13.1 A guide for field testing of relaying current transformer In the application of protective relays, the most widely used input quantity is current. A multiplicity of different protective relays either utilizes current directly, combines it with other currents as in differential schemes, or combines it with voltage to make impedance or power measurements. The source of relay input current is from current transformers which may be located on the bushings of power circuit breakers and power transformers, on the bus bars of metal clad switchgear, or installed as separate items of equipment located as required. Relaying accuracy classes have been established in ANSI/IEEE C57.13-1978, Requirements for Instrument Transformers, to specify the performance of relaying current transformers. During faults on the electric power system, relaying current transformers must operate at high overcurrent levels. ANSI classiÞcations,

MOTORS FOR POTENTIALLY EXPLOSIVE ATMOSPHERE DESIGN SPECIFICATION GUIDE What are the principles for designing explosion-safe electric motors? There are two main principles for explosion protection for electric motors. One is to design the motor so that no dangerous heat or spark occurs. This includes the increased safety version, EEx e. The other method is based on isolating any dangerous heat or spark inside the motor so as to prevent the ignition of any explosive mixture of gases outside the motor. This includes the version with flameproof enclosure, EEx d, and the version with pressurized enclosure, EEx p. These are the three internationally standardized versions that are suitable for motors to be installed in Zone 1. The "non-sparking" version, Exn, according to IEC 79-15 (1987) is intended for use in Zone 2. IEC 79-15 has not yet been transferred to a national standard, but this is expected to happen after it has been converted into a European standard in CENELEC. Br

ELECTRIC MOTOR SPECIFICATIONS ON TEMPERATURE CLASS AND OTHER TEMPERATURE RELATED CONSIDERATIONS GUIDE How to specify electric motors using temperature class as basis? Combustible gas or vapor and explosion-protected electrical equipment is divided into temperature classes T1 to T6 with regard to the ignition temperature of the gas or vapor and the maximum surface temperature of the equipment. Refer to Table1.4A - Temperature Class. Ignition temperature, thermal flashpoint, is the lowest temperature of a surface at which a substance ignites on contact with the surface. Hazardous area and zones Hazardous areas are rooms, spaces or areas in which an explosive gas mixture may occur under conditions such that electrical equipment, among other things, may have to meet certain requirements. Hazardous areas are categorized as zones as follows: Zone 0 - An area in which an explosive gas atmosphere is present continuously or is present for long periods. Zone 1 - An area in which an

Authored by: SALWA ALI AHMED    MOHAMMED ABD EL LATIF BADR    ABLA SOLIMAN ATIA Abstract - Reducing the losses of power distribution systems (technical and nontechnical losses) is an absolutely necessary objective in the sound management of any electrical utility and a major stake for the countries concerned and the lenders. The paper describes the context of losses in power distribution systems and deals more specifically with the corresponding diagnostics and implementation of losses reduction plan. Maneuvers include three main measures, these are: minimization of overload, voltage drop and losses, which are the main role in this paper.

DOWNLOAD FREE ETAP SOFTWARE DEMO ON ELECTRICAL POWER SYSTEM SIMULATION ETAP Electrical Power System Software Demo Download here Before buying the actual ETAP11 Software, the company offers a demo version for those newbie in using the software. Also, this would be helpful for students who wants to learn more on power system simulation. This is a 510MB file where you can download it directly to your PC. However, if you have a slow internet connection, a Demo CD mail can also be an option. By requesting an ETAP demo, you will also receive regular newsletters and information on our latest products and services. You will have the option to opt out at any time. Please see our privacy policy. ETAP and its affiliated companies do not sell or disclose any personal information obtained from our site visitors without their consent to any unaffiliated third party for purposes unrelated to servicing their requests, unless required to do so by law or other regulatory authority Download the demo

Authored by: MARINA YUSOFF*, ASNAWI BUSRAH*, MALIK MOHAMAD*, MAU TENG AU** Abstract: - This paper presents an approach to estimate technical losses in utility’s distribution network based on feeder’s load profile and characteristics, such as such as length, peak demand to installed capacity ratio, and load distribution profile. The developed methodology is implemented in spread sheets format, which is simple and user friendly. It requires minimum set of input data, while giving reasonably accurate results. The approach is tested on a real TNB distribution network and the results are reasonably accurate. Additionally, the spread sheet developed based on the methodology could also be used to perform various energy auditing exercises.

VOLTAGE TRANSFORMERS ROUTINE TEST PROCEDURE C57.13.5 Test procedures for voltage transformers. Applied voltage test on the neutral terminal With the ground link temporarily removed from the neutral terminal of the transformer, a voltage of 19 kV (r.m.s.) shall be applied between the neutral terminal and the ground for 60 s. The gas pressure of the gas-filled transformer may be at any setting equal to or less than the pressure given in Clause 5 for the test. The transformer shall be considered as having met the requirements if no external and internal disruptive discharge or collapse of voltage is observed. Accuracy test The test shall be performed in accordance with 8.1 of IEEE Std C57.13-1993. The calibration of the test system given in 4.3 shall apply. The gas pressure of the gas-filled transformer may be at any setting for the test. The transformer shall be considered as having met the requirements if the performance is within the limits of the accuracy class. Excitation ch

CURRENT TRANSFORMERS ROUTINE TEST PROCEDURE C57.13.5 Test procedures for current transformers. Inter-turn overvoltage test The test shall be performed in accordance with one of the following procedures. If there is no agreement between the manufacturer and user, the choice of the procedure shall be left to the manufacturer. If secondary protective devices are provided, these devices shall be installed for the inter-turn overvoltage test. Procedure A With the secondary windings open-circuited (or connected to a high impedance device which reads the peak voltage), a substantially sinusoidal current shall be applied to the primary winding. The test current shall be increased until one of the following conditions is reached:    a) The r.m.s. value of the applied current is equal to the maximum primary current corresponding to the continuous thermal current rating factor (RF), or    b) The peak value of the secondary induced voltage is equal to:       1) 280 V for metering rated cur

STANDARD REQUIREMENTS IN DEALING WITH VOLTAGE TRANSFORMERS What is a Voltage Transformer with respect to C57.13? Terms in which ratings shall be expressed The ratings of a voltage transformer shall include:      a) Basic impulse insulation level in terms of full-wave test voltage      b) Rated primary voltage and ratio      c) Frequency (in Hertz)      d) Accuracy ratings      e) Thermal burden rating Standard burdens Standard burdens for voltage transformers for rating purposes are shown in table below. Assignment of accuracy ratings A voltage transformer shall be assigned an accuracy rating for each of the standard burdens for which it is rated. For example, an accuracy rating might be 0.3W and X, 0.6Y, 1.2Z. Accuracy classification for voltage transformers with two secondary windings or tappedsecondary windings - The burden on any two secondary terminals affects the accuracy on all other terminals. The burden stated in the accuracy ratings is the total burden on the

STANDARD REQUIREMENTS IN DEALING WITH CURRENT TRANSFORMERS What is a Current Transformer with respect to C57.13? Terms in which ratings shall be expressed The ratings of a current transformer shall include:     a) Basic impulse insulation level in terms of full-wave test voltage.     b) Nominal system voltage, or maximum system voltage.     c) Frequency (in Hertz)     d) Rated primary and secondary currents.     e) Accuracy classes at standard burdens.     f) Continuous thermal current rating factor based on 30 °C average ambient air temperature.     g) Short-time mechanical current rating and short-time thermal current rating. Standard burdens Standard burdens for current transformers with 5 A rated secondary current shall have resistance and inductance according to table below. Accuracy ratings for metering A current transformer for metering shall be given an accuracy rating for each standard burden for which it is rated. For example, the accuracy ratings assigned to

CONVERT NEMA TO IEC ELECTRIC MOTOR ENCLOSURE CLASSIFICATION TUTORIALS How to convert NEMA to IEC  motor enclosure classification? NEMA enclosure classifications are developed by NEMA and used in the U.S./American market. Ingress Protection - IP - ratings are developed by the European Committee for Electro Technical Standardization (CENELEC) (described IEC/EN 60529), and specifies the environmental protection and enclosure provided. The table below can be used to convert from NEMA Enclosure Types to IEC Enclosure Types: source: 2010 IIEE Technical Manuals

EXPLOSIONPROOF MOTOR ENCLOSURE FORMAT DEFINITION How to group explosionproof motor according to its format? The explosionproof motor is a totally enclosed machine and is designed to withstand an explosion of specified gas or vapor inside the motor casing and prevent the ignition outside the motor by sparks, flashing or explosion. These motors are designed for specific hazardous purposes, such as atmospheres containing gases or hazardous dusts. For safe operation, the maximum motor operating temperature must be below the ignition temperature of surrounding gases or vapors. Explosionproof motors are designed, manufactured and tested under the rigid requirements of the Underwriters Laboratories. Hazardous location motor applications are classified by the type of hazardous environment present, the characteristics of the specific material creating the hazard, the probability of exposure to the environment, and the maximum temperature level that is considered safe for the substance crea

ENCLOSURE TYPE FOR ELECTRIC MOTOR SPECIFICATIONS How do they specify the enclosure of an Electric Motor? The enclosure of the motor must protect the windings, bearings, and other mechanical parts from moisture, chemicals, mechanical damage and abrasion from grit. NEMA standards MG1-1.25 through 1.27 define more than 20 types of enclosures under the categories of open machines, totally enclosed machines, and machines with encapsulated or sealed windings. The most commonly used motor enclosures are open dripproof, totally enclosed fan cooled and explosionproof. The Standards for IP Codes apply to the classification of degrees of protection provided by enclosure for all rotating machines. The designation used for the degree of protection consists of the letter IP (International Protection) followed by two characteristic numerals. When the degree of protection is specified by only one numeral, the omitted numeral is replaced by the letter X. For example, IPX5 or IP2X. The first Ch

INSTRUMENT TRANSFORMER THEORETICAL DISCUSSIONS Basic theoretical concept of instrument transformers guide Instrument transformer is the standardized term used for current and voltage transformer. Theoretical Reminder: Current Transformers Current transformers have a similar composition to "conventional" transformers. A magnetic circuit (generally made of an iron alloy) in the shape of a toroid is surrounded by N1 turns on the primary and N2 turns on the secondary. The primary can be reduced to a simple conductor passing through the toroid (n1 = 1) (see figure 6-2). General Application Rule Current transformers feed measuring, control and monitoring devices. Galvanic insulation electrically seperates the primary circuit from the secondary circuit. It allows earthing of the electrical measuring device and thus ensures safety of operating personnel. The current transformer is designed to give the secondary a current that is proportional to the primary current. The seondary

IMAGES OF VOLTAGE TRANSFORMERS INCLUDING TYPES AN DEFINITIONS Images and Illustration of a typical voltage transformer for medium and high voltage level. A voltage transformer or potential transformer is an instrument transformer intended to have its primary winding connected in shunt with a power supply circuit, the voltage of which is to be measured or controlled. A cascade-type voltage transformer is a single high-voltage line terminal voltage transformer with the primary winding distributed on several cores with the cores electromagnetically coupled by coupling windings and the secondary winding on the core at the neutral end of the highvoltage winding. Each core of this type of transformer is insulated from the other cores and is maintained at a fixed potential with respect to ground and the line-to-ground voltage. A double-secondary voltage transformer is one that has two secondary windings on the same magnetic circuit insulated from each other and the primary. Either or

IMAGES OF CURRENT TRANSFORMERS INCLUDING TYPES AN DEFINITIONS Images and Illustration of a typical current transformer for medium and high voltage level. A current transformer is an instrument transformer intended to have its primary winding connected in series with the conductor carrying the current to be measured or controlled. The ratio of primary to secondary current is roughly inversely proportional to the ratio of primary to secondary turns and is usually arranged to produce either five amperes or one ampere (IEC Standard) in the full tap of the secondary winding when rated current is flowing in the primary. Bar: A bar-type current transformer is one that has a fixed, insulated straight conductor in the form of a bar, rod, or tube that is a single primary turn passing through the magnetic circuit and that is assembled to the secondary, core, and winding. Bushing: A bushing-type current transformer is one that has a round core and a secondary winding insulated from an

INSTRUMENT TRANSFORMERS SERVICE CONDITIONS FOR OPERATION What are the conditions that are considered in choosing instrument transformers? The standard ratings of instrument transformers are based on operation at the thermal rating of the instrument transformer for defined ambient temperature conditions provided the altitude does not exceed 1000 meters (3300 feet). Instrument transformers may be used at higher ambient temperatures, at altitudes higher than 1000 meters, or for other unusual conditions if the effects on performance are considered. Consult the manufacturer for specific applications. Altitude: A higher standard BIL may be required at high altitudes in order to obtain the insulation required for the voltage used. The decreased air density at higher altitudes also affects heat dissipation and the permissible loading on instrument transformers. Current transformers may be operated at altitudes greater than 1000 meters if the current is reduced below rated current by 0.3 p

BASIC INSTRUMENT TRANSFORMER INFORMATIONS AND DISCUSSIONS TAKEN FROM STANDARD HANDBOOK FOR ELECTRICAL ENGINEERS How does instrument transformers being use in the power system? The discussion that follows is a short summary of information on instrument transformers as measurement elements. For more extensive information, consult American National Standard C57.13, Requirement for Instrument Transformers; American National Standards Institute; American National Standard C12, Code for Electricity Metering; Electrical Meterman’s Handbook, Edison Electric Institute; manufacturer’s literature; and textbooks on electrical measurements. AC range extension beyond the reasonable capability of indicating instruments is accomplished with instrument transformers, since the use of heavy-current shunts and high-voltage multipliers would be prohibitive both in cost and power consumption. Instrument transformers are also used to isolate instruments from power lines and to permit instrument circuits t