> Abstract: Everybody knew limits flow
pattern circuit breaker the minute to break the ability very high, may
achieve 150-200KA, but here produces the data often is anticipated
short-circuits the magnitude of current, certainly is not is actual
through limits the flow pattern circuit breaker to short-circuit the
magnitude of current, therefore when uses limits which the flow
pattern circuit breaker to protect the electrical power distribution
system verification moves the thermally stable, must pay attention to
the short-circuit current parameter which chooses. Some
factories declared their low-voltage circuit-breaker completely limits
the flow pattern circuit breaker, everybody limits the flow pattern
circuit breaker after the understanding to limit flows the principle,
may distinguish really falsely.
Key word: Limits flows the question load switch fuse
1st, limits the flow pattern circuit breaker the principle
Everybody knew limits flow pattern circuit breaker the minute to
break the ability very high, may achieve 150-200KA, but here produces
the data often is anticipated short-circuits the magnitude of current,
certainly is not is actual through limits the flow pattern circuit
breaker to short-circuit the magnitude of current, therefore when uses
limits which the flow pattern circuit breaker to protect the
electrical power distribution system verification moves the thermally
stable, must pay attention to the short-circuit current parameter
which chooses. Some factories declared their low-voltage
circuit-breaker completely limits the flow pattern circuit breaker,
everybody limits the flow pattern circuit breaker after the
understanding to limit flows the principle, may distinguish really
falsely. Which the low-voltage circuit-breaker limits flows the
question is for divide breaks, it which which the low impedance large
capacity transformer and unceasingly develops the power distribution
network to cause the very big breakdown short-circuit current proposed
requests circuit breaker the minute to break the time to be short
sufficiently enables the short-circuit current in to achieve in front
of its anticipated peak value the minute breaks. At the end of
the 50's, France first studies limits flows the minute to break the
question, and developed has limited flows the air circuit breaker,
caused the air circuit breaker to short-circuit the minute to break
the ability to achieve 100 k A. For several dozens years, some
many kinds are mature, the effect well limit flow the technology to
obtain the widespread use in the low-voltage circuit-breaker, like
goes to the ion grid extinguishing of arc, the limiting resistor, from
duplicate limits flows the part, the magnetism blows, the electrically
operated repulsion, V J C as well as the solid insulation screen
limits flows the technology and so on. At present, in advanced
models the shell type circuit breaker in the design, fully has used
the air electromagnetism principle and limits flows the principle,
causes its minute to break the ability to reach 200 k A. In
recent years, along with the computer technology, the control
technology, the new material technology as well as the electric power
electronic technology introduction, caused to limit flows the
technology to have the renewal development, like the superconductivity
current limiter, take G T O as the foundation current limiter, the
controllable impedance transformer and the failure detection
technology and so on, these limited the class to divide breaks new
technical the research board greatly to enhance the circuit breaker to
divide breaks the ability and limits flows the ability.
The tradition low-voltage circuit-breaker limits flows the
principle which the minute breaks is when the breakdown occurs, the
contact fast opens produces the electric arc, is equal to the string
enters a rapid growth in the line the arc resistance, thus limits the
short-circuit current. This rapid growth arc resistance, usually
is called "the dynamic arc resistance". Is different with the
common circuit breaker explosion chamber, the low pressure limits
flows the circuit breaker the explosion chamber to use many
extinguishing of arc grid piece. In opens breaks in the process,
first 动触?and the static contact separates produces the electric
arc, in electromagnetic field and hot field, under flow field function
movement to extinguishing of arc grid piece. After the electric
arc enters the grid piece, because is divided into many short arcs
nearly extremely the pressure drop, causes the arc voltage rapid rise,
thus achieved limits the class the goal. In order to have the
higher arc voltage, limits flows the circuit breaker explosion chamber
the grid piece number to have to be more than the common circuit
breaker, and arranges closely. The arc voltage rises quickly,
limits flows the effect to be better, final, the arc voltage
surpasses the supply voltage the value, causes the supply voltage to
be unable to maintain the electric arc, thus completes 熄弧 limits
flows the minute to break. Must cause the arc voltage rapidly to
elevate, the tradition has two methods: (1) blow-out coil.
In this kind of situation, the electric arc could rapidly pull
long, it not only increased the electric arc length, moreover also
will increase the electric arc the heat conduction area. (2)
uses directs the arc road to come rapidly to elevate the arc voltage.
When the contact opens, along will direct arc on the
electromagnetic force to pull the long electric arc, when the electric
arc is actuated the explosion chamber, will be able further to divide,
cooling, this method premise request: (1) The electric arc
must be able to force to be separated from the contact (is bigger than
gap when contact between approximately 1 m m, it only then can occur);
(2) The electric arc must extremely quickly be separated
from the contact area, like this reduced the contact material loss,
simultaneously, contact gap restoration; (3) The electric
arc must along direct an arc movement by the extremely quick speed
(approximately 100 m/s), then enters the ion grid piece to enhance the
final arc voltage value.
In limits flows the circuit breaker in the design, has following
4 basic principles:
The a contact rapidly opens
B rapidly enhances the arc voltage
C causes the final arc voltage value to be high
D fast dielectric strength restoration.
Commonly used limits flows the technology to divide three kinds:
1) is artificial 零点? Produces the artificial zero
spot using the electric arc, causes in the arc crack the electric
current is zero, thus causes the electric arc to extinguish.
2) enhances the electric arc static state to bend down - the
Anter law. Usually uses the ion grid law, the insulation grid
law, the narrow stitching and the VJC law and so on. Goes to the
ion grid law is divides the short arc using the wire netting piece the
electric arc which certain mutually connects, uses the short arc the
pressure drop to enhance the arc voltage to cause the electric arc to
extinguish; Insulation grid law: Namely the grid piece is
the insulation, its function is derives the electric arc the quantity
of heat, enhances the electric arc the arc column pressure,
simultaneously, the grid piece divides the electric arc certain
sections the short arc, each grid piece is the short arc electrode,
simultaneously has many anodes pressure drops and the negative pole
pressure drop, the direct class electric arc says, uses the near
极处 electric arc loss of voltage to add the arc column the loss of
voltage together extinguishing of arc; The narrow stitching,
usually uses multiple 窄缝 upside, like this, may reduce the
electric arc enters 窄缝 the resistance, thus assigns when the
actuation electric arc movement electromagnetic force, may use
compared to a list 窄缝 explosion chamber smaller slit, on the one
hand may the electric arc diameter compression, cause the electric arc
with the slit wall close contact; On the other hand, also makes
the electric arc area to increase, the length grows, these all further
strengthened the function which cooling and drifts away, causes the
electric arc to extinguish; The VJC law mainly is in the
electrode all around cover certain thickness insulating material or
the high rheotan material, thus carries on the control to the electric
arc arc column, achieved elevates the arc voltage the goal. The
solid insulation screen law is uses a solid insulation screen fast to
insert to the minute breaks the fault current in the contact, causes
the electric arc which between the contact burns by the screen to
separate but rapidly extinguishes. Above these method usual
synthesis uses, if VJC and the narrow stitching, obtains well limits
flows the effect which the minute breaks.
3) enhances the contact minute to break the speed law. The
usual use huge separation spring or other accelerating devices pull
open the contact, or induces the turbulent flow using the stored
energy capacitor to the repulsion coil electric discharge in the
aluminum plate to produce the huge electrically operated repulsion,
动触?will open, at the same time, will speed up the trip as far
as possible the movement and the organization movement, achieved the
high speed minute will break goal, like this, when separation will
need the time slightly, then will limit flows the function to be
bigger. In the 60's, the electric power electronic device on is
introduced in the electric appliance. Now, whether there is
contact crystal thyratron circuit breaker, did the contact - crystal
thyratron parallel mixed style circuit breaker obtain the development
in certain countries, and has the certain degree the application, but
because the electric power electronic device existence leads passes
the energy consumption which the pressure drop greatly creates high,
divides the circuit breaker not to be able to form the gap insulation
distance, the overload capacity difference, the operational parameter
lacks the corresponding each voltage rank as well as the expense is
high, these enable its constitution the non- electronic contact
electric appliance massively to apply. Certainly, non-
electronic contact electric appliance itself has the operation rate
high, the shutter speed quick, the control power small, the noise is
low, the life long characteristic, suits certain special work
situation uses. In limits flows, mainly uses belt contact the
mixed style, when the contact - crystal thyratron parallel mixed style
circuit breaker, has the contact normally leads passes the pressure
drop energy consumption small characteristic, again opens using the
electric power electronic device breaks the time short characteristic,
further reduces the electric current to open breaks the time, thus
realizes limits flows the minute to break. In the circuit
breaker design, the electrification electronic device, mainly must
consider the component the electric current and the voltage parameter.
Early use crystal thyratron, but it cannot from shut off, needs
to trade the class to shut off, creates the electric appliance the
volume to increase. At present, the usual consideration from the
component which shuts off, like IGBT (insulation grid bipolar
transistor), GTO (may shut off transistor) and so on.
2. The high pressure limits the flow pattern fuse and the
low score breaks between the ability electric appliance the selective
coordination.
In this kind of service condition, limits the flow pattern fuse
act under the big fault current, the low score breaks between the
ability electric appliance only to be able to divide breaks it to
allow the minute to break 小电? therefore needs according to two
different time - current curve coordination realization. 1/ take
the curve 相交?as a dividing line, limits the flow pattern fuse
to undertake the big fault current minute to break, other electric
appliances undertake the normal electric current and the glitch
electric current start break. 2/ if other electric appliances
not along with fuse ram interconnection 脱扣, then 相交?must be
bigger than the high pressure to limit the flow pattern fuse most
petty action electric current. 3/ curve 相交?electric
current must be smaller than other electric appliances to open breaks
the ability. 4/ when limits the flow pattern fuse open circuit
with the high pressure, other electric appliances must have enough
gather the short-circuit current through the short-circuit current and
the pass the ability (to verify this electric appliance thermally
stable, move stable correspondence to use its drop-out current, pass
gather electric current), these abilities should limit the flow
pattern fuse closure electric current and the I2t value with the high
pressure adapt. 5/ if other electric appliances along with fuse
ram interconnection 脱扣, for example load switch, then the request
load switch permits the shift magnitude of current is bigger than the
fuse biggest shift magnitude of current. |
