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[Utility / T&D Automation & Engineering Magazine, p35]

Transformer - Information required with enquiry and order "CHECKLIST" (IEC 60 076-1)

The list is not exhaustive.

I- Normal Information:

N°	INFORMATION	YES	NO
1	Particulars of the specifications to which the transformer shall comply (e.g : international & national standards, …)
2	Kind of transformer (separate winding, auto-transformer or booster)
3	Single or three-phase unit
4	Number of phases in system
5	Frequency
6	Dry-type (degree of protection) or liquid filled (mineral oil or synthetic insulating liquid) "see IEC 60529
7	Indoor or outdoor type
8	Type of cooling
9	Rated power (on the ONAN / ONAF)
10	Rated voltage for each winding
11	For a transformer with tappings : (see IEC 60 076-1)
-	Which winding is tapped
-	The number of tappings, and
-	The tapping range or tapping step
-	"Off - Circuit" or "On - Load " tap-changing is required
-	If the tapping range is more ± 5% :
-	The type of voltage variation (Constant Flux Voltage Variation, Variable Flux Voltage Variation or Normal operation is CbV V : Combined Voltage Variation)
-	The location of the maximum current tapping
12	Higest voltage for equipment (Um) for each winding (see IEC 60 076-3)
13	Method of system earthing (for each winding)
14	Insulation level (see IEC 60 076-3)
15	Connection symbol and neutral terminals (e.g : Y, Z or D …)
16	Any peculiarities of insulation, assembly, transport and handling. Restrictions on dimensions and mass
17	Details of auxiliary supply voltage (for fans and pumps, tap-changer, alarms, etc)
18	Fittings required and an indication of the side from which meters, rating plates, oil level indications, shall be legible
19	Type of oil preservation system
20	Capitalisation of losses.

II- Special Information:

N°	INFORMATION	YES	NO
1	If a lightning impulse voltage test is required, whether or not the test is to include chopped wavec (IEC 60076-3).
2	Whether a stabilizing winding is required and, if so, the method of earthing (neutral not isolated, limit the zero sequence impedance)
3	Short-circuit impedance, or impedance range
4	Tolerances on voltage ratios and short-circuit impedances as left to agreement in IEC 60076-1 table 1, or deviating from values given in the table
5	Whether a generator transformer is to be connected to the generator directly or through switchgear, and whether it will be subjected to load rejection conditions which can give up to 1.4 times normal voltage in 5 seconds
6	Whether a transformer is to be connected directly or by a short length of overhead line to gas-insulated switchgear (GIS) Also connection of large power transformer with high current isolated phase bus duct has to be mentrioned
7	Altitude above sea level, if in excess of 1000 m (3300 ft)
8	Special ambient temperature conditions (see IEC 60076-1 section 1.2.1b), or restrictions to circulation of cooling air.
9	Expected seismic activity at the installation site which requires special consideration
10	Special installation space restrictions which may influence the insulation clearances and terminal locations on the transformer also the maintenance
11	Whether load current wave shape will be heavily distorted. Whether unbalanced three-phase loading is anticipated. In both cases, details to be given.
	Load with abnormal harmonics current, harmonic factor above 5%, may cause excessive losses and abnormal heating.
	Other special operation conditions such as :
	Continuous load operation at voltage and voltage per Hertz avove 105% of rated values, and above 110 % in no-load condition.
	Continuous operation at load power factor less than 80%
12	Whether transformers will be subjected to frequent over-currents
13	Details of intended regular cyclic overloading other than covered by IEC 60076-1 clause 4.2 (to enable the rating of the transformer auxiliary equipment to be estabilished)
14	Any other exceptional service conditions (unusual strong magnetic fields)
15	If a transformer has alternative winding connections, how they should be changed and which connection is required ex works
16	Short-circuit characteristics of the connected systems (expressed as short-circuit power or current, or system impedance data) and possible limitations affecting the transformer design (see IEC 60076-5)
17	Whether sound-level measurement is to be carried out (see IEC 60551)
18	Vacuum withstand of the transformer tank and, possibly, the conservator, if a specific value is required.
19	Any tests not referred to above which may be required.
20	Any information ragarding the required corrosion resistance or colour of the surface treatment in reference to the geographic zone and pollution zone has to be stated

III- Parallel Operations:

If parallel operation with existing transformers is required, this shall be stated and the following information on the existing transformers gives :

N°	INFORMATION	YES	NO
1	Rated power
2	Rated voltage ratio
3	Voltage ratios corresponding to tappings other than the principal tapping
4	Load loss at rated current on the principal tapping, corrected to the appropriate reference temperature
5	Short-circuit impedance on the principal tapping and at least on the extreme tappings, if the tapping range of the tapped winding exceeds ±5%
6	Diagram of connections, or connection symbol, or both

Note: On multi-winding transformers, supplementary information will generall be required

Automatic Capacitor Bank Sizing

 The following calculator is used to determine the capacitor kVAR required to improve PF of a single load or entire power system.

Actual power factor, peak kilowatt demand, desired PF and system voltage are required.  The best source for this information is the monthly utility bill or other local monitoring equipment.  

A calculation of each months data for a 12 month period is recommended to determine the maximum kVAR required.

Click the link bellow to download the Automatic Capacitor Bank Sizing Calculator (an .xls file written by Schneider Electric)

http://ul.to/40mls5tv

Basic Electrical Concepts

In each plant, the mechanical movement of different equipments is caused by an electric prime mover (motor). Electrical power is derived from either utilities or internal generators and is distributed through transformers to deliver usable voltage levels. 

Electricity is found in two common forms:

• AC (alternating current) 

• DC (direct current). 

 Electrical equipments can run on either of the AC/DC forms of electrical energies. The selection of energy source for equipment depends on its application requirements. Each energy source has its own merits and demerits.
 Industrial AC voltage levels are roughly defined as LV (low voltage) and HV (high voltage) with frequency of 50–60 Hz.

An electrical circuit has the following three basic components irrespective of its electrical energy form:
• Voltage (volts)
• Ampere (amps)
• Resistance (ohms).

Voltage is defined as the electrical potential difference that causes electrons  to flow.
Current is defined as the flow of electrons and is measured in amperes.
Resistance is defined as the opposition to the flow of electrons and is measured in ohms. 
All three are bound together with Ohm’s law, which gives the following relation
between the three:

V = I × R

Where

V = Voltage
I = Current
R = Resistance.

Power

In DC circuits, power (watts) is simply a product of voltage and current. 

P =V × I 

For AC circuits, the formula holds true for purely resistive circuits; however, for the following types of AC circuits, power is not just a product of voltage and current.
Apparent power is the product of voltage and ampere, i.e., VA or kVA is known as apparent power. Apparent power is total power supplied to a circuit inclusive of the true and reactive power. 
Real power or true power is the power that can be converted into work and is measured in watts.
Reactive power If the circuit is of an inductive or capacitive type, then the reactive component consumes power and cannot be converted into work. This is known as reactive power and is denoted by the unit VAR.

Relationship between powers

Apparent power  (VA) = V × A

True power (Watts) =  VA × cos Φ

Reactive power (VAR) = VA × sin Φ 

Power factor

Power factor is defined as the ratio of real power to apparent power. The maximum value it can carry is either 1 or 100(%), which would be obtained in a purely resistive circuit.

                        True power
Power factor =  -------------------
                            Apparent power   
          

Percentage voltage regulation

                              (No load voltage - Full load voltage)
% Regulation = 100 ----------------------------------------
                                Full load voltage

Electrical energy
This is calculated as the amount of electrical energy used in an hour and is expressed as follows:

Kilowatthour = kW× h

Where
kW = kilowatt
h = hour.

Types of circuits
There are only two types of electrical circuits – series and parallel. 
A series circuit is defined as a circuit in which the elements in a series carry the same current, while voltage drop across each may be different. 
A parallel circuit is defined as a circuit in which the elements in parallel have the same voltage, but the currents may be different.

[a useful article from "Practical Troubleshooting of Electrical Equipment
and Control Circuits" ]

Periodic Table of the Elements

Periodic Table of the Elements

H

He

Li

Be

B

C

N

O

F

Ne

Na

Mg

Al

Si

P

S

Cl

Ar

K

Ca

Sc

Ti

V

Cr

Mn

Fe

Co

Ni

Cu

Zn

Ga

Ge

As

Se

Br

Kr

Rb

Sr

Y

Zr

Nb

Mo

Tc

Ru

Rh

Pd

Ag

Cd

In

Sn

Sb

Te

I

Xe

Cs

Ba

La

Hf

Ta

W

Re

Os

Ir

Pt

Au

Hg

Tl

Pb

Bi

Po

At

Rn

Fr

Ra

Ac

Unq

Unp

Unh

Uns

Uno

Une

Ce

Pr

Nd

Pm

Sm

Eu

Gd

Tb

Dy

Ho

Er

Tm

Yb

Lu

Th

Pa

U

Np

Pu

Am

Cm

Bk

Cf

Es

Fm

Md

No

Lr

Name	Number	Weight
Melts		Freezes

---

Legend
Metals	A solid substance that is a good conductor of eat and electicity. Can be formed into many shapes.
Metalloid	"Middle elements" - conduct heat and electricity better than nonmetals, but not as well as metals. Easier to shape than nonmetals, but not as easy as metals. Solid at room temperature.
Nonmetals	A poor conductor of heat and electricity. Not easily formed into shapes.