Design of a residual current circuit breaker ICwith anti-interference technique

Cheng Peng • Yan Han • Zhen-Qi Fan •

Wen Fu • Xing-Gan Guo

Received: 5 October 2008 / Revised: 1 September 2009 / Accepted: 23 November 2009 / Published online: 31 December 2009

� Springer Science+Business Media, LLC 2009

Abstract Residual current circuit breakers (RCCB) is the

equipment which protect human body from an electric

shock, there is close relation between RCCB and human

safety. However, shortages still exist. Current RCCB tend

to cause nuisance tripping due to their sensitive reaction to

the interference signal in the actual power grid. So, the

RCCB cannot work at the crucial moment effectively. This

paper analyzes the impact to the RCCB from the general

interference signal and induced interference signal in

power grid, and this paper also introduces a new tech-

nique—10 ms non-actuating time technique, which is used

to stand aside the interference signal. This technique with

delay time protection and other anti-interference technique

are integrated into a special RCCB IC chip, which is fab-

ricated in a mixed-signal 0.5 lm CMOS process in CSMC.

The test results verify great improvement in RCCB per-

formance. Additionally, this paper analyzes the disadvan-

tage of the active national standard referring to RCCB in

China and presents some suggestions for the improvement.

Keywords RCCB � Anti-interference � IC

1 Introduction

With the rapid development of economics and increasing

demand of electricity, more and more electrical equipments

are used in people’s daily life. So residual current circuit

breaker (RCCB) is widely used to prevent human body

from electrical shocks [1]. However, in low-voltage power

network, there are many interference signals which may

trigger the RCCB unexpectedly. Without considering the

interference signals, the existing RCCB using imported IC

(such as M54123) and other imitated IC always show a

high rate of nuisance tripping, which seriously reduced the

practical installation rate of RCCB. Thus there arises a

necessary demand to enhance the anti-interference ability

of RCCB. This paper analyzes the lighting induced inter-

ference signal in power grid firstly, and then points out the

shortages of the active national standard referring to RCCB

in China. Based on the analysis, a new method is developed

which can help RCCB stand aside the lighting induced

interference signal, greatly improving the anti-interference

performance of RCCB. And at last a novel integrated cir-

cuit with this technique and other interfere with the auto-

matic identification techniques are designed and

implemented in 0.5 lm CMOS process. At last, the test is

successful. The chip has Independent intellectual property

rights.

2 Interference signals analysis

There are many kinds of interference signals in the low-

voltage power network, one of them is induced by lightning

strike, and this interference signal is most likely to cause

nuisance tripping of RCCB.

The principle of indirect lightning induced interference

signal is showed in Fig. 1, when the lightning strikes near

the phase line, the electromagnetic field radiated by the

lightning causes Lightning Electromagnetic Pulse (LEMP),

then the LEMP is coupled to the phase line and cause

induced voltage. The amplitude of induced voltage varies

from several kilovolts to tens of kilovolts and duration time

C. Peng � Y. Han (&) � Z.-Q. Fan � W. Fu � X.-G. Guo

Department of Information Science and Electronics Engineering,

Institute of Microelectronics and Optoelectronics, Zhejiang

University, PO Box 1269, 310027 Hangzhou, China

e-mail: hany@zju.edu.cn

123

Analog Integr Circ Sig Process (2010) 64:199–204

DOI 10.1007/s10470-009-9430-7

is about 50 ls [2]. This induced voltage will trigger the

lightning arrester to operate and release the energy to the

ground. However, once the lightning arrester operates,

the current path becomes low-impedance, and the voltage

in phase line will cause a current to ground. This phe-

nomenon is called power frequency freewheeling. The

current will not disappear until the phase angle of voltage

in the phase line crosses zero, and then the lightning

arrester will turn back to high-impedance state. According

to the definition, the current going from phase line to

ground is defined as residual current, which is just the

interference signal, and its duration time will not exceed

half cycle of power frequency (10 ms).

3 Disadvantage of the active national standard

The purpose of using RCCB is to protect people from

electronic shock, so it is very important to make sure the

RCCB can give a proper protection to human body. So the

national standard is formulated in order to regulate the

RCCB product market. National Standard of RCCB is

identical to International Electro-technical Commission

Standard IEC61008-1[Residual Current Operated Circuit

breakers without Integral Over-current Protection for

Household and Similar Uses (RCCB’s); Part 1: General

Rules], two types of RCCB is introduced for residual

current protection, one is normal type, the other is S type,

the relationship between trip time and residual current is

presented in Table 1 [2] (IDn=30 mA).

In Table 1, we can find out that both normal type pro-

tection and S type protection have limiting break time, but

only S type protection has limiting non-actuating time. So

in the market for direct contacting RCCB, the most popular

residual current protection integrated circuit is M54123

which opens the circuit in 0.006 s after the residual current

reaches IDn, there is no non-actuating time in this chip.

However, there are many interference signals such as the

lighting induced interference signal analyzed before

existing in low-voltage power network, so the nuisance

tripping rate of the RCCB using M54123 is high and this

situation affects the regular service of RCCB.

By considering the actual situation, this paper propose an

improvement suggestion for national standard, which is

adding at least 10 ms non-actuating time in normal type

direct contacting protection RCCB, this method will greatly

reduce the nuisance tripping rate and improve the real

installation rate of RCCB. So the electric shock accidents

for the missing of RCCB at a crucial moment will reduce.

The new specifications of RCCB IC’s trip time and non-

actuating time are given in Table 2.

The limiting break time in Table 2 only defines the trip

time of RCCB IC, and the total trip time of RCCB has to be

Neutral Line

Phase Line

LoadInduced Voltage

Lighting Arrester

Lighting

Fig. 1 Principle of indirect lighting induced interference signal

Table 1 Standard value of trip time and non-actuating time

Type Rated current In½A� Residual current I0Dn½A� Standard value of trip time and non-actuating time when residual current equals or

exceeds following values (in seconds)

IDn 2IDn 5IDn 5A,10A,20A,50A,

100A,200A,500A

Normal type Any value Any value 0.3 0.15 0.04 0.04 Limiting break time

S type C25 [0.030 0.5 0.2 0.15 0.15 Limiting break time

0.13 0.06 0.05 0.04 Limiting non-actuating time

Table 2 Specifications of new

RCCB IC’s trip time and non-

actuating time

Type IDn 2IDn 5IDn 5A,10A,20A,50A,

100A,200A,500A

Normal type 0.200 0.080 0.013 0.013 Limiting break time

0.150 0.060 0.010 0.010 Limiting non-actuating time

S type 0.300 0.150 0.080 0.080 Limiting break time

0.250 0.120 0.060 0.060 Limiting non-actuating time

200 Analog Integr Circ Sig Process (2010) 64:199–204

123

about 0.02 s longer than Table 2 because of mechanical

time delay.

4 Design of the integrated circuit [3, 4]

This new RCCB integrated circuit includes two major

functional parts: residual current protection and over-volt-

age protection. The block diagram is shown in Fig. 2.

According to Fig. 2, the chip is a typical mixed-signal

system, including the analog part and digital part. The main

function of the analog part is to provide suitable working

environment for the whole chip and pre-process the

residual current signal, the main function of digital part is

to intelligently remove the interference in the residual

current signal by some digital processing algorithm.

When a residual current signal inputs (V1), it is firstly

sent into low-pass filter to get rid of high frequency

Fig. 2 Function block diagram of the RCCB IC

Fig. 3 Signal processing flow

simulated by Cadence

Analog Integr Circ Sig Process (2010) 64:199–204 201

123

interference, and then the residual current signal is ampli-

fied (V2) and compared with some internal reference

voltage, the result signal (V3) is output to the digital part.

In the digital part, through judging the continuity and pulse

width of the signal it identify whether the input signal is

another interference signal (not a lighting induced inter-

ference signal), which can avoid nuisance tripping. [5, 6].

Then an output current driver module provides enough

current to trigger the external SCR to cut off the power

line. The signal processing flow simulated by Cadence is

shown in Fig. 3.

The realization of 10 ms non-actuating time for lighting

induced interference signal is based on the strategy below:

when the residual current exceeds 5IDn, the chip starts a

10 ms timer. When the 10 ms timer counts down to zero, if

there is no other residual current signal sensed by RCCB

IC, that means the residual signal RCCB sensed is a

interference signal which lasts no more than 10 ms; if there

is another residual current sensed by RCCB IC when the

10 ms timer counts down to zero, that means the contin-

uous signal is right the residual current, so the chip will cut

off the power line immediately. The simulation result of

10 ms non-actuating module is showed in Fig. 4.

5 Test result

The chip is fabricated in 0.5 lm CMOS mixed-signal

process technology in CSMC. Including the IOPAD (with

ESD) and core, the die size is 0.9 mm2. The total current of

the chip is 400 lA with a 5 V supply, so the powerFig. 4 Simulation result of 10 ms non-actuating module

Fig. 5 Layout of RCCB IC

202 Analog Integr Circ Sig Process (2010) 64:199–204

123

consumption is 2 mW. The layout picture of the chip is

shown in Fig. 5.

The function test result of the residual current protection

is shown in Fig. 6, Curve 1 is residual current signal

detected by the RCCB IC, and Curve 2 is the output signal

to trigger the SCR. The gap between Curve 1 and Curve 2

is the delay time (T = 0.2 s), The chip is working in

Normal type.

Figure 7 is the test result of 10 ms non-actuating time

function, in Fig. 7, Curve 1 is residual current signal which

amplitude exceeds 5IDn, if the residual signal only lasts half

cycle, the output signal Curve 2 keeps low, and if the

residual signal is continuous longer than two half cycle, the

output signal jumps to high after detecting the second half

of residual current signal.

6 Conclusion

In this paper, a residual current circuit breaker IC incor-

porated with many techniques to reduce the nuisance

tripping. These techniques are based on the analysis to the

serious interference signals in low quality power network,

utilizing digital circuit technology, and the function of

Intellectualized estimating and accurate delay time is

integrated into a new RCCB IC. The chip has independent

intellectual property rights. The test result indicates that the

RCCB IC can eliminate the interference signal and reduce

the nuisance tripping rate effectively, and accord with the

national standard. After the promotion, it will have great

social and economic benefits.

We have reason to believe that the new conditions

demand more in line with the RCCB national standards in

the near future will be issued and implemented smoothly.

References

1. Jankov, V. (1997). Estimation of the maximal voltage induced on

an overhead line due to the nearby lighting. IEEE Transactions onPower Delivery, 12(1), 315–324.

2. GB16916-2003. Residual current operated circuit-breakers with-out integral over-current protection for household and similar uses(rccb’s); part 1: General rules.

3. Razavi, B. (2000). Design of analog CMOS integrated circuits.

New York: McGraw-Hill, Inc.

4. Allen, P. E., & Holberg, D. R. (2002). CMOS analog circuit design(2nd ed.). Oxford: Oxford University Press.

5. Han, Y., Wang, Z., Yu, H., & Xie, J. (2005). A novel multi-

functional leakage current protector IC design. Chinese Journal ofSemiconductor, 26(8), 1537–1542.

6. Pan, H., & Han, Y. (2006). Design of a smart leakage current

protector IC. Microelectronics, 36(4), 518–521.

Cheng Peng was born in

Hunan, China, in 1986. He

received the B.S. degree in

electronics science and technol-

ogy from Zhejiang University,

Hangzhou, China in 2008.

Presently, he is working toward

the M.S. degree in microelec-

tronics at Zhejiang University,

Hangzhou. His research inter-

ests are in the area of mixed

analog/digital system integrated

circuit design and simulation.

Fig. 6 Test result of residual current protection

Fig. 7 Test result of 10 ms non-actuating time function

Analog Integr Circ Sig Process (2010) 64:199–204 203

123

Yan Han was born in Beijing,

China, in 1959. She received the

B.S. degree in electrical engi-

neering from Zhejiang Univer-

sity, Hangzhou, China in 1982,

and the Master degree and the

Ph.D. degree in engineering

from the same university in

1990 and 1995, respectively.

After graduation she became the

Member of faculty of Zhejiang

University, and majored in

semiconductor device and inte-

grated circuit design. In 1996

she became an Associate Pro-

fessor and since 2003 she had been a Professor in Zhejiang Univer-

sity. More than 50 papers and two books were published. Prof. Han

now is the vice director of Microelectronics Institute of Zhejiang

University.

Zhen-qi Fan was born in Fuj-

ian, China, in 1985. He received

the B.S. degree in electronics

engineering from Southeast

University, Nanjing, China in

2008. Presently, he is working

toward the M.S. degree in

microelectronics at Zhejiang

University, Hangzhou. His

research interests are in the area

of mixed analog/digital system

integrated circuit design and

simulation.

Wen Fu was born in Jiangxi,

China, on March 9th, 1984. He

received the diploma in micro-

electronics and Master degree

from Zhejiang University,

Hangzhou, China, in 2006 and

2008, respectively. From 2006

to 2008 he developed integrated

circuits primarily for residual

current circuit breaker (RCCB)

in Institute of Microelectronics,

Zhejiang University. In 2008, he

joined Galaxycore Microelec-

tronics Corporation in Shanghai.

His major research area is pixel

design and process integration for CMOS image sensor.

Xing-gan Guo was born in

1939. He was a senior engineer

at the Institute of Rural Electri-

fication in Ministry of Water

Resources and one of leakage

protection panel members of the

State Grid Corporation of

China. He also participated in

drawing up the GB6829-1995

(General requirements for

residual current operated pro-

tective devices) and in the

preparation of human SD219-

1987 (Leakage protection

device installation and operation

procedures in rural areas).Meanwhile he is the main drafter of the

SL445-2009 (Leakage protection device installation and operation

procedures).

204 Analog Integr Circ Sig Process (2010) 64:199–204

123