Section 4
1MAC050144-MB C
Protection functions
300
615 series ANSI
Technical Manual
(Equation 17)
I
highest measured phase current
I
ref
the set value of the
Current reference
setting
T
ref
the set value of the
Temperature rise
setting (temperature rise (°C) with the steady-state current I
ref
The ambient temperature value is added to the calculated final temperature rise estimation.
If the total value of temperature is higher than the set trip temperature level, the
PICKUP
output is activated.
The
Current reference
setting is a steady-state current that gives the steady-state end
temperature value
Temperature rise
. It gives a setting value corresponding to the rated
power of the transformer.
The
Temperature rise
setting is used when the value of the reference temperature rise
corresponds to the
Current reference
value. The temperature values with the
corresponding transformer load currents are usually given by transformer manufacturers.
Thermal counter
49T applies the thermal model of two time constants for temperature measurement. The
temperature rise in degrees Celsius (°C) is calculated from the highest of the three-phase
currents according to the expression:
(Equation 18)
ΔΘ calculated temperature rise (°C) in transformer
I
measured phase current with the highest TRMS value
I
ref
the set value of the
Current reference
setting (rated current of the protected object)
T
ref
the set value of the
Temperature rise
setting (temperature rise setting (°C) with the steady-state current
I
ref
)
p
the set value of the
Weighting factor p
setting (weighting factor for the short time constant)
Δt
time step between the calculation of the actual temperature
t
1
the set value of the
Short time constant
setting (the short heating / cooling time constant)
t
2
the set value of the
Long time constant
setting (the long heating / cooling time constant)
The warming and cooling following the two time-constant thermal curve is a characteristic
of transformers. The thermal time constants of the protected transformer are given in
seconds with the
Short time constant
and
Long time constant
settings. The
Short time
constant
setting describes the warming of the transformer with respect to windings. The
Long time constant
setting describes the warming of the transformer with respect to the oil.
Using the two time-constant model, the IED is able to follow both fast and slow changes
in the temperature of the protected object.
The
Weighting factor p
setting is the weighting factor between
Short time constant
τ
1
and
Long time constant
τ
2
. The higher the value of the
Weighting factor p
setting, the larger is
Θ
final
ref
ref
I
I
T
=
⎛
⎝
⎜⎜
⎞
⎠
⎟⎟ ⋅
2
ΔΘ
Δ
=
⎛
⎝
⎜⎜
⎞
⎠
⎟⎟
⎡
⎣
⎢
⎢
⎢
⎤
⎦
⎥
⎥
⎥
⋅ −
⎛
⎝
⎜
⎜
⎞
⎠
⎟
⎟
+
−
(
)
⋅
−
p
I
I
T
e
p
ref
ref
t
*
*
2
1
1
1
II
I
T
e
ref
ref
t
⎛
⎝
⎜⎜
⎞
⎠
⎟⎟ ⋅
⎡
⎣
⎢
⎢
⎢
⎤
⎦
⎥
⎥
⎥
⋅ −
⎛
⎝
⎜
⎜
⎞
⎠
⎟
⎟
−
2
2
1
Δ
Содержание 615 Series ANSI
Страница 1: ...Relion Protection and Control 615 series ANSI Technical Manual ...
Страница 2: ......
Страница 29: ...1MAC050144 MB C Section 615 series ANSI 22 Technical Manual ...
Страница 389: ...Section 4 1MAC050144 MB C Protection functions 382 615 series ANSI Technical Manual ...
Страница 485: ...Section 6 1MAC050144 MB C Supervision functions 478 615 series ANSI Technical Manual ...
Страница 635: ...Section 10 1MAC050144 MB C Other functions 628 615 series ANSI Technical Manual ...
Страница 707: ...Section 15 1MAC050144 MB C Applicable standards and regulations 700 615 series ANSI Technical Manual ...
Страница 711: ...Section 16 1MAC050144 MB C Glossary 704 615 series ANSI Technical Manual ...
Страница 712: ......