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Functions of Instrument Transformers (CTs and PTs)

AC type protective relays are actuated by the current and voltage supplied by the current and potential (voltage) transformers which are generally classified as instrument transformers. Generally instrument transformers are used for mainly two purposes. For metering purpose which steps down and displays voltage and current levels from kV to (0-110 volts in case of PT) and few kilo amps to (0-5 amps in case of CT) . Second purpose is to supply current and voltage magnitudes to the relays to carryout protection functions.

The main functions of instrument transformers are:

  • Instrument transformers (current and potential transformers) provide insulation against the high voltages of the power circuit and to protect the apparatus and the operating personnel from contact with the high voltages of the power circuits
  • Instrument transformers (CTs and PTs) supply protective relays with current and voltages of magnitude proportional to those of the the power circuits. These current and voltage magnitudes supply by the instrument transformers are sufficiently reduced such that the relays can be made relatively small and inexpensive
  • Instrument transformers helps in attaining different types of secondary connections to obtain the required current and voltages

For proper applications of CTs and PTs required considerations are:

Mechanical construction , type of insulation (dry or liquid), ratio in terms of primary and secondary currents or voltages, continuous thermal rating, short time thermal and mechanical ratings, insulation class, impulse level, service conditions, accuracy and connections

For the safety purpose, the secondaries of the current and potential transformers (CTs and PTs) are grounded.

Why Instrument Transformers Used and Advantages

Voltmeters and Ammeters are used to measure the voltage and current in the circuits. Using instrument transformers ranges of these devices to measure can be increased. A current transformer is bascially a step down transformer hence it steps down the current. When used in conjunction with the low range ammeter, a current transformer (CT) increases the range of the ammeter. Thus a 0-5A ammeter can be used to measure several hundreds or thousand amperes of current. Similarly a potential transformer (PT), which is basically a step down transformer can increase the range of the low voltage voltmeter. Thus a voltmeter designed to measure voltage upto 110V can measure a much higher voltages (several thousnd volts) when used in conjnction with suitable potential transformer

Instrument transformers have many advantages. Some of the advantages are given below:

Advantages:

  • Single range ammeters and voltmeters can measure a wide range of currents and voltages, if used in conjunction with suitable Current Transformers (CTs) and Potential Transformers (PTs)
  • The measuring instruments like ammeter, voltmeter and wattmeters etc are incorporated in the secondary circuit and hence they are totally segregated from the high voltage, thereby ensuring safety for the operator and observer
  • The meter need not be insulated for high voltages which would be the case if they are directly included in a high voltage circuit
  • Using current transformer with suitable split and hinged core, it easy to measure heavy currents in the busbarwithout having to break the conductor carrying current. The core of the Current Transformer (CT) is opened at the hinge, the current carrying conductor is introduced in the center of the core through a opening made and the core is tightly closed again. The conductor itself acts as a single turn primary winding of the current transformer
 * Above Documents Sourced from Inst Tools
Posted in Energy Management By Electrical Supply Store

WHAT IS MBUS? AND HOW IS IT USED IN METERING SYSTEMS?

August 23, 2021

Necessity is the mother of invention, they say but in the case of MBus, it was frustration that drove Professor Dr. Horst Ziegler of the University of Paderborn, who, in cooperation with Texas Instruments Deutschland GmbH and Techem GmbH. Developed the Meter-Bus or M-Bus protocol. 

WHAT IS AN M-BUS OR METER BUS?

The M-Bus concept was based on the ISO-OSI Reference Model, in order to realize an open system that could utilize almost any desired protocol. Today, M-Bus is ideal for sub-metering because it simplifies the communication between smart metering devices and the gateway or Data Collection Unit in the building allowing for the frequent collection of meter readings for energy management, or utility billing. This meter reading technology created in Europe is gaining popularity in North America with a wide variety of applications when it comes to submetering.

Let us take a closer look at what M-Bus is all about.

It is a serial communication system that uses a single pair of conductors that can tie up to 250 slaves, in this case, meters: to a single master, gateway, or in our case a Data Collection Unit. Every meter is then connected to the bus. The M-Bus string is exceptionally insensitive to external interference that may be caused by capacitive or inductive coupling. It can power the communication module on the meter, while electrically isolating it from other external sources, and it is a very cost-effective method for wiring in buildings, particularly when compared to Pulse-Output meters.
In addition to the savings in the initial installation costs, servicing the system is also easier, as any addition of a meter can be done without the need for reconfiguration of a daisy chain and there is further simplification because M-Bus incorporates protection against reversed polarity.

ROLE OF MBUS IN THE METERING SYSTEM

Metering systems, in particular, those that meter flow, like water or Thermal Energy (heat)meters, use M-Bus to transmit energy consumption via a field bus (the Meter Bus) to a Master.
The communication is simple because the size of the information to transmit is small it can be transmitted up to one kilometer between the meter and the Data Collection Unit, provided the M-Bus voltage is maintained, once in operation; more than one meter can simultaneously and accessible on one common platform, making data available for energy-efficiency purposes.

HOW MBUS IMPROVES METERING SYSTEM PERFORMANCE

M-bus systems have come a long way from manual reading methods where an employee from the metering company would have to read the data in hard-to-reach areas of the building - A previous time-consuming method that was often measured at long intervals. With M-Bus one, many or all the meters can be interrogated (polled) at any one time, or periodically, this is advantageous when tenants or occupants move in the middle of a billing period, and a partial period reading of the meter is required.
M-Bus can be programmed for multiple Baud rates from 300, to 38,400 Bauds, although most operators will settle with 9,600 Bauds.

MBUS PROVIDES FAST AND ACCURATE REMOTE DATA

Mbus reads measurements electronically at shorter intervals, allowing landlords to have a more accurate view of tenant consumptions. The ability of MBus technology to read data faster from virtually anywhere eliminates manual reading errors made by field personnel.

OFFERS THE POSSIBILITY OF EXPANSION

While each master has a maximum of 250 slaves, there is no theoretical limit on the number of masters that can be installed this provides added benefits for future troubleshooting, for instance, in a large apartment building the water metering for Domestic Cold Water can be segmented from the Domestic Hot Water meters, allowing for additions to each of these systems at a later date. Another option is to retrofit and add another bus for another utility, like for Thermal Energy metering without disturbing the existing buses, and integrating all into a single reporting platform.

GET RELIABLE ELECTRONIC READINGS

Compared to pulse-output meters, M-Bus is more accurate because it transmits the value of the actual read from the meter, and not the pulse count, avoiding using multipliers for conversion, which ensures the availability precise data. Additionally, the M-Bus wire-runs present higher immunity to noise and electromagnetic interference that may affect pulse transmission through non-shielded wiring.

SAVES COSTS

Unlike pulse output meters the MBus wiring is simpler and uses less cable.  

* Above document is sourced from our supplier Intellimeter

Posted in Energy Management By Electrical Supply Store

WHAT IS SUBMETERING

2021-08-24 3:47:53 PM

WHAT IS SUBMETERING

December 07, 2018

The rising costs of energy are impacting businesses across the globe. Companies worldwide are facing an uphill battle with these rising prices, in some cases being hit with hikes of up to 120%, as opposed to 20% increases faced by regular households. Trends show that these figures will continue to grow.

Sub-metering allows landlords, homeowners associations, multi-headquartered companies, property managers and any other type of multi-tenant property owners or associations to monitor their utilities. It also offers the ability to organize and bill the utility usage. It is especially useful when it comes to dividing electrical, gas, or water bills for several buildings, apartments, offices, or even individual tenants. Sub-metering is mostly used for electricity meters, gas meters and water meters, Which are utilities found on any type of building.

WHY SHOULD I OPT FOR SUB-METERING?

First thing’s first! If you want to have the most efficient energy consumption, be it electrical, gas, or water; sub-metering is without a doubt the easiest and most cost-effective method to reduce expense and to correctly track monthly utilities.

“I recommend that master-metered residential buildings currently [in Con Edison’s service territory] be required to submeter each dwelling unit within four years...” • NY Dept. of Public Service Staff testimony in Con Edison rate case September 2008

When it comes to larger spaces or entire condominium associations, sub-metering proves itself to be even more efficient, cutting costs even more. It is since the more apartments, offices, or buildings are metered together; the more significant the chances are that consumption losses will not be tracked down. It means that losses will be harder to track and analyze. Without the possibility of tracking down the source of energy losses, solving the problem becomes exponentially more difficult and costlier.

You can monitor the total electric, gas or water consumption for the entire building and also track the individual components of that consumption, with the added flexibility of being as detailed or granular as a single appliance, like HVAC, refrigerators, TV sets or any load whether indoor or outdoors.

Installing a sub-meter will let you understand and monitor consumption patterns for any specific buildings or equipment.

WHAT ARE THE MOST IMPORTANT BENEFITS OF SUB-METERING?

From a business perspective, the benefits of sub-metering include:

  • Separates energy use in facilities that receive funds from different sources, e.g., state-supported vs. auxiliary, instruction vs. research, academic vs. hospital
  • Facilitates charge-backs1 to departments or other campus units as a way to encourage energy efficiency measures.

From an engineering perspective, the benefits of sub-metering include:

  • Identifies performance improvements and guides preventive maintenance: trends in the monthly and annual use of each form of energy help to identify the benefits received from system upgrades and also the energy systems (e.g., boilers or chillers) that may need attention if they show unexpected increases in use.
  • Enables quick response to failures of system components, assuming the meters are linked to an energy management system (EMS).

From a management perspective, the benefits of sub-metering include:

  • Assists in making decisions about energy upgrades in buildings by comparing energy use in similar facilities.
  • Focuses accountability for building operations on the facilities department, encouraging building managers to control energy consumption. Facilities department staff review metered data, know which buildings consume a disproportionate amount, and can be held accountable. The data facilitates the dialog and collaboration between the energy manager and the building users (or tenants) in finding ways to reduce consumption, leading to increase efficiency in operations.

Sub-metering is cost-efficient and eco-friendly because it helps in lowering energy consumption and unwanted costs. The lower the energy loss, the bigger the profits and the greener the environment. If that’s not a good enough reason to install a sub-meter, then maybe the reasons listed below will convince you that sub-metering is a must for any building or building complex.

Sub-metering offers:

  1. A precise and accurate overview of your energy consumption in real-time
  2. A very detailed review of energy data regarding any monitored facility
  3. Access to historical records needed when failures appear or to schedule preventive maintenance
  4. The ability to record your entire real energy usage
  5. A more efficient decision-making process when optimizing energy consumption per unit/apartment/equipment/building/complex.
  6. An overview in real-time along with the historical of the consumption of the monitored area
  7. Ability to identify and fix the sources of energy loss.

It is clear that Sub-metering offers accountability for utilities usage and provides tools that lead to reduced consumption. Take the first step towards managing your energy costs. Re-examine your current setup and make improvements.

* Above document is from our supplier Intellimeter Canada Inc.

Posted in Energy Management By Electrical Supply Store

Automatic Door Opener Name Chart

2020-02-18 1:42:00 AM

More and more electricians install automatic door opener for swing doors now. The automatic door opener is a new field to most electricians, if you haven't installed any before, it is tough and difficult for you, especailly you maybe do not know how to order it.

What's the meaning of Left hand pull (LPL), right hand pull (RPL), left hand push (LPS), right hand push (RPS), how to tell it? If you asks the sales guy, everybody gives different answer which confuses you too much.

Don't worry, Aurora Lighting designed the following Automatic Door Opener Name Chart. Look at the chart, there are only 8 combonations for single swing door installation, you just need tell us which photo number matches your application, right away you will have the right model number for the door opener.

 

Posted in Safety Products By Aurora Lighting

Lets you determine the amperage or the KVA according to the parameters that are known. You must choose the number of phases and give at least two (2) of the three (3) parameters of the equation to get a result.

EVI Line Card - 1 phaseEVI Line Card - 3 phase

Posted in Ballast & LED Driver By Ballast & Transformer Team

How to convert kW to kVA

2017-08-31 1:42:00 AM

How to convert real power in kilowatts (kW) to apparent power in kilovolt-amps (kVA).

kW to kVA calculation formula

The apparent power S in kilovolt-amps (kVA) is equal to the real power P in kilowatts (kW), divided by the Power Factor PF:

S(kVA) =  P(kW) PF

So kilovolt-amps are equal to kilowatts divided by the power factor.

kilovolt-amps = kilowatts / PF

or

kVA = kW / PF

Example

What is the apparent power in kilovolt-amps when the real power is 3 kW and the power factor is 0.8?

Solution:

S = 3kW / 0.8 = 3.75kVA

Posted in Ballast & LED Driver By Ballast & Transformer Team

Isolation Transformer

Transformers with primary (input) and secondary (output) windings separated from each other are known as isolation transformers. Under this construction, the input power and the output power are electrically separated by an dielectric insulation barrier.

 

Isolation Transformer Winding Diagram

Isolation Transformer

 

 

Advantages of using an isolation transformer

  • The primary and secondary winding can be constructed as a step-up or step-down transformer to match the load in the electrical system
  • Preventing the equipment from getting spikes and harmonics from the mains
  • Safety. There will be no conductive connection between the live part of the circuit and earth. With the isolating transformer, there is no danger in touching the live while the body is earthed.
  • By connecting the electrical system safety ground to the neutral conductor on the transformer secondary, it eliminates neutral-to-ground voltage and noise. This resolves reliability problems for microprocessor-based electronics.

Isolating transformers are also the most common kind of transformers for voltage step-up and step-down usage.However, 1:1 ratio transformers, where input and output voltage are the same, are also widely used to solely take advantage of the isolation.


Autotransformer

Step-down Autotransformer

Step-up Autotransformer
Step-down Autotransformer Step-up Autotransformer

 

In an autotransformer, the primary and secondary share a common winding. The secondary voltage always has a common terminal with the primary. Step up or down of the voltage is achieved by a tap from the winding measuring from the common end. For example, a secondary tap at 50% of the winding will produce a voltage half of the input.

Advantages of using an Autotransformer

  • Lighter in weight and smaller in physical size as it requires fewer windings and a smaller core.
  • Less costly compared to an isolation transformer.
  • The advantages listed typically are for autotransformer with voltage ratio ranging up to 3:1 voltage or vice versa. Beyond this range, an isolation transformer is usually more economical.

Limitations

  • There is no isolation between the primary winding and the secondary winding. Therefore protection of the equipment is dependant on the supply devices.
  • As the primary and secondary share a common end, if the neutral side of the primary voltage is not grounded, the secondary side will not be either.
  • A failure of the winding insulation of the autotransformer will result in full input voltage applied to the output.
Posted in Hold-Tite Fasteners Hand Dryer - FAQs By Ballast & Transformer Team

About Leviton OBC AFCI Receptacles

As a market leader in electrical wiring devices, Leviton has introduced an OBC AFCI Blank Receptacle which addresses the dangers associated with both types of potentially hazardous arcing – parallel and series arcing. Similar to GFCIs, AFCI receptacles provide feed-through protection and are able to detect downstream parallel and series arc-faults, as well as upstream series arc-faults. Utilizing an AFCI receptacle offers homeowners the benefit of localized Test and Reset, providing a convenient option to AFCI breakers.

 

The Difference between AFCI and GFCI outlets

AFCIs and GFCIs are both important devices to incorporate into a home’s electrical system. It is important to recognize, however, that although they are similar in appearance they offer very different protection. The AFCI blank receptacle is designed to provide protection from electrical fires that could result from arc-faults, whereas the GFCI receptacle protects people from potentially hazardous shocks and electrocution. Additionally, GFCI receptacles are required in wet or damp locations such as kitchens, bathrooms, basements, laundry rooms and garages. AFCI receptacles are often required in family rooms, dining rooms, living rooms, parlors, libraries, dens, bedrooms, sunrooms, recreation rooms, closets and hallways.

Posted in Safety Products By Leviton Product Support

How to install Floor Heating

2016-06-04 1:51:52 AM

Floor Heating and Snow Melting for Professionals 

Danfoss is the leading manufacturer of intelligent electric floor heating systems and outdoor systems for ice and snow melting.
 
This position is secured by a dedicated focus on advanced and above all user friendly systems, developed in the world’s largest competence center for floor heating. 

Read More
Posted in Heating & Cooling By Danfoss Sales Rep
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