1
(webers/meter
2
)
e
N
d
1
dt
1
1
N
P
edt
e
2 E sin(7t)
1
2 E
N
7
cos(
7t)
1
max
2 E
N
7
x
1
2
%f
V
N
1
max
x
1
2
%N
V (volts)
f (hertz)
BE1-24 General Information
1-1
SECTION 1 • GENERAL INFORMATION
PURPOSE
BE1-24 Volts Per Hertz Overexcitation Relays are specifically designed to protect transformers, generators
and iron core reactors from the adverse effects of excessive heating resulting from overexcitation.
Overexcitation exists whenever the per unit volts per hertz exceeds the equipment design limitations.
OVEREXCITATION
Overexcitation is excessive flux density in the magnetic core of the protected equipment. Once the magnetic
core is at or near saturation, any increase in the applied voltage will cause the excess flux to travel outside
the core through the air or the structural steel components. Structural steel components are not laminated,
and stray flux in these components cause large eddy current losses and hysteresis losses. This generates
excessive heat. Also, the excess flux through the air requires a large current in the winding which creates
excessive heat.
Overexcitation of transformers, iron core reactors, and generators can cause severe damage. This
overheating causes the deterioration of adjacent insulation, and if allowed to persist, will lead to equipment
failure. Modern designs are especially sensitive to overexcitation because they operate with high flux
densities. Overexcitation can result from an increase in voltage or a decrease in frequency.
VOLTS PER HERTZ PRINCIPLE
Protective relaying must determine the level of flux density from the secondaries of voltage and/or current
transformers. The following demonstrates the relationship between the actual flux density, voltage, and
frequency as monitored by the protective relays.
By Definition, Flux Density:
(1)
Faraday’s Law:
(2)
Therefore:
(3)
Let:
(4)
Then:
(5)
And:
(6)
Therefore:
(7)
Summary of Contents for BE1-24
Page 9: ...1 4 BE1 24 General Information Figure 1 1 Inverse Square vs Two Step...
Page 10: ...BE1 24 General Information 1 5 Figure 1 2 Protection Characteristics of the BE1 24...
Page 12: ...BE1 24 General Information 1 7 Figure 1 3 Style Number Identification Chart...
Page 16: ...BE1 24 General Information 1 11 Figure 1 4 Inverse Square Characteristic Curves...
Page 19: ...2 2 BE1 24 Human Machine Interface Figure 2 1 Location of Controls and Indicators...
Page 27: ...4 2 BE1 24 Installation Figure 4 1 M1 Case Outline Dimensions Front View...
Page 30: ...BE1 24 Installation 4 5 Figure 4 4 M1 Case Double Ended Panel Drilling Diagram Rear View...
Page 31: ...4 6 BE1 24 Installation Figure 4 5 M1 Case Panel Drilling Diagram...
Page 32: ...BE1 24 Installation 4 7 Figure 4 6 M1 Case Projection Mounting Outline Dimensions Rear View...
Page 34: ...BE1 24 Installation 4 9 Figure 4 7 Typical Internal Connections...
