2016 International Conference on Condition Monitoring and Diagnosis - Xi'an - China
Feasibility analysis of impedance monitoring method for Turn-to-turn Insulation Fault of Dry-type Air-core Reactor Hong L1U,Yonghong WANG,Ziwei G AO,Xuecheng ZHU Harbin University of Science and Technology,Heilongjiang Electric Power Research Institute Harbin 150080,150030 Heilongjiang Province, China Email:
[email protected] [email protected] Abstract-Dry-type Air-core Reactor consists of multi-layer
ection and unbalanced three-phase protection method,the turn
coils and Multi-strand windings.The change of impedance value
to-turn fault of dry-type air-core reactor cannot be detected in
caused by turn-to-turn insulation fault of dry-type air-core rea
time.!n general,turn-to-turn insulation fault cannot be found
ctor is so little that the over current protection and Three-phase
until the reactor appears smoke,even fire burning,and the
imbalance protection can't act timely.In order to monitor turn
turn-to-turn insulation fault develops into phase-to-phase short
to-turn insulation fault of reactor , a new monitoring method ba
circuit or phase-to-ground short circuit.Therefore, it is necess
sed on impedance variation is proposed in this paper. Takes
ary to carry out research on the dry-type air-core reactor
reactor BKK-20,OOO/63 for an example to study the relation
protection.
between the variation of impedance value and the turn-to-turn
At present,the technology of oil-immersed type reactor
insulation fault position of dry-type air-core reactor. The result
protection is relatively mature ,and commonly used method is
shows that the change of equivalent reactance value caused by
through comparing the zero sequence compensation voltage of
turn-to-turn insulation fault is little,while the change of equi
end with the zero sequence voltage of head-end of the reactor
valent resistance value is large. The closer the axial fault to both
to detect turn-to-turn fault, which is not applicable for dry type air-core reactor[2-31.Some scholars put forward a protec
ends is, the larger the variation is. Along with the radial fault location, variation of outer is larger than inner's. Method based
tion method,which is based on variation of voltage ratio ,for
on the variation of resistance to monitor the turn-to-turn insul-
the turn-to-turn fault of dry-type series reactor. The ratio of
ation fault of dry-type air-core reactor is feasible. Besides,the rel
the voltage on the capacitor and reactor is a constant value
ative monitoring method based on loss or tangent of dielectric
under normal circumstances,which will change when there is a short circuit fault on the reactor[4-51. It is not applicable for
loss angle is reasonable.
dry-type air-core reactor either.There is no mature protection
Keywords: Dry-type air-core reactor; Turn-to-turn insulation;
methods and techniques for the dry-type air-core reactor at
Monitoring; Impedance variation
present. 1.
INTRODUCTION This paper analyzes the variation of electrical parametes
Dry-typr air-core reactor has advantages of simple stru
of dry-type air-core reactor,when reactor turn-to-turn insulat
cture,light weight,convenient maintenance,etc,Which is used
ion fault happens,and discusses the monitoring method of turn
to balance the reactive power and improve the voltage quality in the electrical power system[11.However,the fault incidence
-to-turn fault of dry-type air-core reactor based on it. II.
rate of dry-type air-core reactor is higher than the transformer and other equipments' under the same voltage grade. A large
(1) Equivalent circuit
amount of data analysis indicates that the main eason of
Actually, multi-layer reactor turn-to-turn insulation fault
dry-type air-core reactor fault is turn-to-turn insulation fault.
circuit that occurs in the early stage is strand-to-strand insu
Currently, due to the low sensitivity of overcurrent prot-
978-1-5090-3396-6/16/$3\.00 ©2016 IEEE
CALCULALATION METHOD
lation fault. Under the condition of power-frequency , dry-
152
type air-core reactor is combination of multi-parallel branches,
p(2nRini + hi)
each branch has a DC resistance, self inductance and mutual
n
inductance. A reactor is provided with n layers, and each layer is provided with m strand coils. When a short circuit occurs in the i-th layer of the strand coils, the coil can be divided into 2
eter of aluminum wire, h;is the height of layer coil.
it of tum-to-tum insulation fault reactor,which consists of n-J branch based on layer coil and I branch based on strand coi
(3) Voltage equations
I,as shown in figureI-I.R; and L; respectively represent bra
When the reactor is applied to the voltage U , and each
nch resistance and self inductance, mutual inductance exists between each branch.As shown in Figure1-1.
i,
R,
R�
(;
L,
r
i
. R,,
U,
L2
L,
RQ
t
io
i.
O J Ro [ R
LB •
R" LA
[;,
r' "
J
LiS
(3)
Wherep is the resistivity of aluminum wire, d)s the diam
short circuit units and the remaining unit.The equivalent circu
i,
( ; )2
branch current is Ii ,the voltage matrix equation of equivalent
in-1
i,
R"j
R;IJ
circuit under normal condition can be obtained by the formula(4) RI + jeoLI jeoMIl .. , jeoMl,; .. , jeoM21. R2 + jeoL2 .. , jeoM2; .. ,
L,
L",
jeoMI,. jeoM2;
i, i2
U
jeoM;2 .. , jeoM",J .. , R" + jeoL" j"
U
U
ii4 jeoM;J
Fig.l-l The equivalent circuit of dry-type air-core reactor
(4)
When the strand-to-strand fault occurred between coils,
(2) Parameter calculation method
the fault coils are divided into five parts, the circuit equations
Neumann formula can be used to calculate mutual
as follows:
inductance between each coil.
. . . . jOJMn.JI +"'+(�I + jOJLn)Jn +... + jOJMn.in =U1 .
.
.
.
jOJMi2il +"'+(�2 + jOJLi2)Ii2 +... + jOJMi2.in =U2 (1) Where,
Z, ,
HI 2
H2 2
=----
+S
,
Z
4
H
1
= __
2
H
.
+_2 +S
Ii!
2
.
Ii
Coil self-inductance can be calculated by the formula(2). L
=
2Jlon2R2 [F(R,R,H)-F(R,R,O)]
. + =
Ii3
=
.
Iii
.
Ii2
. +
. +
Ii2
Ii4
.
+
(5)
Ii5
(4) Calculation ofImpedance
(2)
Tolal Current of reactor can be calculated by sum of each
Where, Rj and R2 are the two radius of coils,HjandH2are
layer current.
the heights of coils,njandn2are the numbers of tums.xjandx2are the distances from two coil turns to the center of the coil,1l ois
(6)
vacuum magnetic permeabilitY,and S is the distance between two coils center.
Total impedance can be calculated by the formula(7).
The coil conductor resistance depends on the size of the conductor geometry size,which can be obtained by the formu la(3). 153
when strand-to-strand short circuit occurs at the end is larger
U Z=----;-= R+ jX I ·
than on other heights of reactor. All statistical results shows (7)
that the variation of the layer coil current is in the range of
Equivalent resistance and equivalent reactance are given
-4.63%�3.61%, and variation of layer coil current is larger than the total current .Take the 41-th layer coil as an example,
by formula(8)
layer coil current variation of a short circuit occurred on
R = ReCZ)
different heights of the reactor is shown in Figure 2-2 .
X = ImCZ)
(8)
The current and the equivalent impedance can be calcul ated by Matlab software. III.
THE RESULAT OF CALCULATION
(1) Reactor impedance check
This paper takes a BKK-20000/63 reactor as an example
Sequence of Laycr coils
to calculate,which is composed of 11 packages, 49 layers of coils, and each layer of coil is made up of 2 strands of wires in
Fig. 2-2The relative variation of layer coil current
parallel. Factory provides a detailed structural parameters about the reactor.
With a strand coil as a unit, the variation of short circuit
According to the formula (4), the impedance value of the
strand coils current as shown in figure2-3. Strand coils current
faultless reactor is 67.9483. Factory-fresh reactor impedance
changes significantly, and two groups of them are in pairs for
is 68.1196, and the calculated value error is 0.25%.
that short circuit circles formed in the side of coils. The biggest changes in the amount can up to 10424.
(2) Result of current calculation
12(){){)
Take l-st, ll-th, 21-th, 31-th, 41-th, 49-th layer coils
---'-i l-coil
(from the inside to the outside)of reactor for short circuit
_i2_coil """-i3-coil
analysis.When the reactor is applied the rated voltage,and
_i4_coil
short circuit respectively occurs at the coil 0 (end), 1/8, 1/4, 3/8 and 1/2 at the height (Center)of reactor, the total coil current variation as shown in figure 2-1. When short circuit occurs at the end of the coil, the change of the total current is the largest, with the short
0.00
position of the short circuit moving to the center, the change
0.13
Positon of short ci rcuit 0.25
0.38
0.50
Fig.2-3 The relative variation of strand current
of value decreases rapidly. Besides,the total current variation (3) Impedance calculation
of outer layer is larger than the inner layer's. However, the
According to formula (8), The equivalent resistance and
change of total current value of reactor is very little, the
reactance variation of reactor when strand-to-strand short
maximum value is
