A single-phase load is supplied through a feeder whose impedance is 95 + j360 N and a 35- kV/2400-V transformer whose equivalent impedance Zeg is 0.23 + j 1.27 Q referred to its low-voltage side. Use the approximate equivalent circuit of the practical transformer. The load is 160 kW at 0.89 leading power factor and 2340 V. Compute the phasor voltage Vs (expressed in polar form, in volts) at the sending end of the feeder. Refer all quantities to the high voltage side. Feoder Transformer Load 95 +j 360 0 160 kW Vs E1 E2 0.89 pf leading V = 2340 + jo v

Power System Analysis and Design (MindTap Course List)
6th Edition
ISBN:9781305632134
Author:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Publisher:J. Duncan Glover, Thomas Overbye, Mulukutla S. Sarma
Chapter3: Power Transformers
Section: Chapter Questions
Problem 3.28MCQ
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A single-phase load is supplied through a feeder whose impedance is 95 + j360 2 and a 35-
kV/2400-V transformer whose equivalent impedance Zeq is 0.23 +j 1.27 N referred to its
low-voltage side. Use the approximate equivalent circuit of the practical transformer. The
load is 160 kW at 0.89 leading power factor and 2340 V. Compute the phasor voltage Vs
(expressed in polar form, in volts) at the sending end of the feeder. Refer all quantities to the
high voltage side.
Feeder
Transformer
Load
95 +j 360 0
160 kW
Vs
E1
E2
0.89 pf leading
VL = 2340 + jo Vv
Transcribed Image Text:A single-phase load is supplied through a feeder whose impedance is 95 + j360 2 and a 35- kV/2400-V transformer whose equivalent impedance Zeq is 0.23 +j 1.27 N referred to its low-voltage side. Use the approximate equivalent circuit of the practical transformer. The load is 160 kW at 0.89 leading power factor and 2340 V. Compute the phasor voltage Vs (expressed in polar form, in volts) at the sending end of the feeder. Refer all quantities to the high voltage side. Feeder Transformer Load 95 +j 360 0 160 kW Vs E1 E2 0.89 pf leading VL = 2340 + jo Vv
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How do I compute voltage at the high voltage terminal of the transformer

 

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Follow-up Question
K
= 95.94 -36.88° A
Therefore the load volt
Vload - Load Zload
(95.94 -36.88° A) (5 236.87⁰ (2)
479.7 Z-0.01° V
And the line losses are given by;
Ploss = (line) ² Ruine
= (9.594 A)²(0.18 (2)
16.7 W
7| Page
a.
b.
4.0 TRANSFORMERS PDF
Notice that by stepping up the transmission voltage of the power system, the transmission losses
have been reduced by a factor of 90. In addition, the voltage at the load dropped significantly in
the system with transformers compared to the system without transformers.
a L
Exercise:
95 + £360
A single-phase load is supplied through a 35-kV feeder whose impedance is
2 and a 35-kV:2400-V transformer whose equivalent impedance is (0.23 +1.27) 22 referred
to its low-voltage side. The load is 160 kW at 0.89 leading power factor and 2340 V.
Compute the voltage at the high-voltage terminals of the transformer.
Compute the voltage at the sending end of the feeder.
Compute the power and reactive power input at the sending end of the feeder.
Main components of a power transformer
The Figure below illustrates a cut-away view of an oil-filled transformer.
The main components of the transformer are as follows:
Core. Provides a route for the magnetic flux and supports the low-voltage and high voltage
windings.
Low-voltage winding. It has fewer turns compared with the high voltage windings. Its conductor
has a large diameter because it carries more current.
High-voltage winding. It has a larger number of turns, and its conductor has a smaller diameter
than the low-voltage winding conductor. The high-voltage winding is usually wound around the
low-voltage winding (only cooling ducts and insulation separate the windings). This is done to
minimize the voltage stress on the core insulation.
Tank. Houses the windings, core, and oil. It must be strong enough to withstand the gas pressures
and electromagnetic forces that could develop when a fault occurs.
Oil. It is a good-quality mineral oil. It provides insulation between the windings, core, and
transformer tank. It also removes the heat generated. The oil is specially refined, and it must be
free from impurities such as water, inorganic acid, alkali, sulphur, vegetable and mineral oil.
Note: Some transformers use askarel, which is a nonflammable insulating and cooling medium
instead of insulating oil. It gives good fire protection, which is a significant advantage when the
transformer is located inside a building. However, askarel contains polychlorinated biphenals
(PCBS). They have been linked to cancer-causing substances.
Therefore, they have been banned. Most industries are now in the process of replacing transformers
containing askarel with dry-type transformers or transformers
containing mineral oil.
Thermometer. Measures the oil temperature and initiates an alarm when the temperature exceeds
the alarm set point.
Low/high-voltage bushing. Ceramic bushing that carries the low/high-voltage conductor and
incula
insulates it from the tank. The high-voltage bushing is usually filled with oil to enhance the heat
removal capability.
8| Page
Low/high-voltage connection. Connects the low/high-voltage conductor to the circuit.
Conservator tank. It contains oil and has the capability of absorbing the swell of the oil when it
becomes hot.
7
Transcribed Image Text:K = 95.94 -36.88° A Therefore the load volt Vload - Load Zload (95.94 -36.88° A) (5 236.87⁰ (2) 479.7 Z-0.01° V And the line losses are given by; Ploss = (line) ² Ruine = (9.594 A)²(0.18 (2) 16.7 W 7| Page a. b. 4.0 TRANSFORMERS PDF Notice that by stepping up the transmission voltage of the power system, the transmission losses have been reduced by a factor of 90. In addition, the voltage at the load dropped significantly in the system with transformers compared to the system without transformers. a L Exercise: 95 + £360 A single-phase load is supplied through a 35-kV feeder whose impedance is 2 and a 35-kV:2400-V transformer whose equivalent impedance is (0.23 +1.27) 22 referred to its low-voltage side. The load is 160 kW at 0.89 leading power factor and 2340 V. Compute the voltage at the high-voltage terminals of the transformer. Compute the voltage at the sending end of the feeder. Compute the power and reactive power input at the sending end of the feeder. Main components of a power transformer The Figure below illustrates a cut-away view of an oil-filled transformer. The main components of the transformer are as follows: Core. Provides a route for the magnetic flux and supports the low-voltage and high voltage windings. Low-voltage winding. It has fewer turns compared with the high voltage windings. Its conductor has a large diameter because it carries more current. High-voltage winding. It has a larger number of turns, and its conductor has a smaller diameter than the low-voltage winding conductor. The high-voltage winding is usually wound around the low-voltage winding (only cooling ducts and insulation separate the windings). This is done to minimize the voltage stress on the core insulation. Tank. Houses the windings, core, and oil. It must be strong enough to withstand the gas pressures and electromagnetic forces that could develop when a fault occurs. Oil. It is a good-quality mineral oil. It provides insulation between the windings, core, and transformer tank. It also removes the heat generated. The oil is specially refined, and it must be free from impurities such as water, inorganic acid, alkali, sulphur, vegetable and mineral oil. Note: Some transformers use askarel, which is a nonflammable insulating and cooling medium instead of insulating oil. It gives good fire protection, which is a significant advantage when the transformer is located inside a building. However, askarel contains polychlorinated biphenals (PCBS). They have been linked to cancer-causing substances. Therefore, they have been banned. Most industries are now in the process of replacing transformers containing askarel with dry-type transformers or transformers containing mineral oil. Thermometer. Measures the oil temperature and initiates an alarm when the temperature exceeds the alarm set point. Low/high-voltage bushing. Ceramic bushing that carries the low/high-voltage conductor and incula insulates it from the tank. The high-voltage bushing is usually filled with oil to enhance the heat removal capability. 8| Page Low/high-voltage connection. Connects the low/high-voltage conductor to the circuit. Conservator tank. It contains oil and has the capability of absorbing the swell of the oil when it becomes hot. 7
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