Hioki IR4053 User manual

Insulation Tester IR4053
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HIOKI Technical Notes Vol. 2 2016 No. 1
measurement. Furthermore, the instrument provides voltage
measurement functionality for measuring voltages of up to
1000 V DC, a capability that is ideal for measuring the no-
load voltage of solar panels.
In addition, the instrument provides ordinary insulation
resistance measurement functionality (with ve ranges)
that complies with Japanese Industrial Standards (JIS)
C1302, allowing measurement of the insulation resistance
of equipment other than solar panels.
The IR4053 is available in two congurations: as the
IR4053-10, which includes standard-type test leads, and as
the IR4053-11, which includes switched test leads, for the
Japanese domestic market.
B. Measurement of Solar Panel Insulation Resistance
The technical report JEM-TR228, Maintenance and
inspection guidelines for photovoltaic power generating
systems up to 50 kW for low-voltage network (Japanese),
published by The Japan Electrical Manufactures’
Association, provides important information about the
maintenance and inspection of solar power systems. The
guidelines describe the measurement methods in addition
to the maintenance and inspection items of small-scale solar
power systems, and they recommend that the insulation
resistance of relay terminal boxes (junction boxes and power
Abstract—The Insulation Tester IR4053 is an insulation
tester designed for use in the maintenance of solar power
system equipment. This paper describes the product’s features,
architecture, and other characteristics.
I. IntroductIon
Due in part to rising awareness of environmental issues,
increasingly serious power shortages, and Japan’s national
initiatives to promote use of solar power in recent years,
there has been rapid growth in use of solar power systems,
from small-scale residential setups to large-scale megasolar
installations. These developments are driving growing
demand for equipment maintenance.
To prevent accidents caused by faulty insulation during
installation and regular inspections of solar power systems,
it is necessary to check the state of insulation by measuring
the insulation resistance at various points in the system.
When using a standard insulation tester to accomplish this
task, the technician must cut off power to the measurement
target before measuring the insulation resistance. In the
case of solar panels, insulation resistance must be measured
while the system is at a dangerous voltage since electricity
is always generated while the system is exposed to sunlight
during the day. Consequently, technicians must exercise a
high level of caution with regard to the hazard of electrical
shock while measuring insulation resistance. In addition,
it is sometimes not possible to obtain accurate resistance
insulation values when a standard insulation tester is used
to test a solar power system because the voltage produced by
the solar panels affects the measurement results.
It was against this backdrop that Hioki developed the
Insulation Tester IR4053 as an instrument that is able to
safely and accurately measure the insulation resistance of
solar panels.
II. overvIew
A. Overview of the IR4053
The IR4053 is a portable digital insulation tester.
Developed to be capable of measuring the insulation
resistance of solar panels safely, accurately, and quickly, it is
ideal for maintenance of solar power systems.
The instrument features a new photovoltaic resistance
function designed specically to measure the insulation
resistance of solar panels. This function makes it possible
to accurately measure insulation resistance free from the
effects of the electricity being produced by the panel under
Insulation Tester IR4053
Takeaki Miyazawa
Engineering Division 5, Engineering Department
Appearance of the IR4053.

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HIOKI Technical Notes Vol. 2 2016 No. 1
collection boxes) and power conditioning systems (PCSs) be
measured as part of both the post-installation inspection and
regular inspections.
Two methods are used to measure the insulation
resistance of solar panels, and they differ in both safety
and accuracy. Whichever method is used, all strings must
be measured. To prepare for measurement, the junction
box’s output disconnect must be turned off to isolate it from
the PCS and power collection box. In addition, all string
switches must be turned off. Each of the two methods is
described below.
1) Method in which P and N are not short-circuited:
Fig. 1 illustrates a measurement method in which P (the
positive electrode) and N (the negative electrode) are not
short-circuited. The insulation resistance between P and
E (ground) is measured, and then the insulation resistance
between N and E is measured. This method is safer than
the method in which P and N are short-circuited, which is
described below. However, in some cases it is not possible
to obtain an accurate insulation resistance value due to
the effect of the voltage produced by the solar cell on
insulation resistance measurement, which results from the
deterioration of the solar panel’s insulation.
2) Method in which P and N are short-circuited: Fig.
2 illustrates a measurement method in which P and N are
short-circuited. A shorting switch is used to short-circuit P
and N, and the insulation resistance between the output of
the shorting switch and E is measured. While this method
yields accurate insulation resistance values, it poses the risk
of daytime electric shock, since that’s when solar panels
operate. In this way, an arc discharge could occur during
work. In addition, abnormal heating may occur when P
and N terminals of a faulty solar panel are short-circuited,
posing a re hazard.
3) Example of the failure of the non-short-circuiting
method to yield accurate measurements: Fig. 3 and Fig. 4
illustrate measurement of the insulation resistance between
P and E when the P terminal is grounded and when the N
terminal is grounded, respectively.
When measuring the insulation resistance between P
and E while the P terminal is grounded, as shown in Fig.
3, there is no route by which current produced by the solar
panel can nd its way to the insulation tester, enabling
accurate measurement. However, when measuring the
circuit with the N terminal grounded, as shown in Fig. 4,
current produced by the solar panel can ow to the insulation
tester. Since current from the instrument and current from
the solar panel ow in the same direction and are added, the
result is that the measured resistance value is less than the
actual insulation resistance. By contrast, if the instrument
is connected such that the direction of the insulation tester’s
current is opposite to that of the solar panel’s current,
the current values are subtracted, with the result that the
indicated measured resistance value is larger than the actual
LINE: −
EARTH: +
Positive terminal
Negative terminal
Insulation
resistance
tester
Bypass diode
Blocking device
Earth
Fig. 1. Method in which P and N are not short-circuited.
PV string
Resistance
(ground fault)
Insulation
resistance
tester
EARTH
LINE
P
N
Measured
current
Earth
For cutoff of solar strings
Earth
Fig. 3. P-E measurement diagram when P is grounded.
PV string
Resistance
(ground fault)
Insulation
resistance
tester
EARTH
LINE
P
N
Measured
current Earth
PV current
For cutoff of solar strings
Earth
Fig. 4. P-E measurement diagram when N is grounded.
LINE: −
EARTH: +
Insulation
resistance
tester
Shorting switch
Earth
Fig. 2. Method in which P and N are short-circuited.

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HIOKI Technical Notes Vol. 2 2016 No. 1
insulation resistance. The IR4053’s photovoltaic resistance
function is able to measure insulation resistance accurately
without being affected by the current produced by the panel,
even when using the method in which P and N are not short-
circuited.
III. FunctIons and Features
A. Photovoltaic Resistance Function
The IR4053’s photovoltaic resistance function can
make accurate measurements even when using the method
in which P and N are not short-circuited. In addition, the
function is safer than the method in which P and N are short-
circuited, and the process can be performed more easily
since there is no need to short the terminals. The applied
voltage can be set to either 500 V or 1000 V.
Large-scale facilities such as megasolar installations
require measurement of large numbers of strings, making
it desirable to keep measurement times short so that work
can be completed more quickly. Since the instrument
displays the measured value within 4 seconds from the start
of measurement when using the photovoltaic resistance
function, the IR4053 is well suited to maintenance work at
large-scale solar power installations.
B. Insulation Resistance Function
The IR4053 also provides an insulation resistance
function with the same measurement performance as
instruments in the previous IR4050 series, allowing its use
in standard insulation resistance measurement applications
in addition to solar panel measurement applications. Five
ranges (50 V, 125 V, 250 V, 500 V, and 1000 V) are available
for selection depending on the specic application at hand,
and measured values are displayed within 1 second of the
start of measurement, ensuring fast measurement.
C. Voltage Measurement Up to 1000 V DC
Technicians measure no-load voltage during maintenance
of solar power systems, and solar power systems operating at
up to 1000 V are becoming increasingly common in Japan.
The IR4053 provides a voltage function that can measure
voltages of up to 1000 V DC, allowing its use in inspecting
the no-load voltage of these 1000 V systems.
D. Negative Voltage Warning Function
The IR4053 also provides a negative voltage warning
function that causes the screen to ash red if the voltage
measurement function yields a negative voltage measured
value. During system installation, technicians measure
voltage in order to check the no-load voltage and wiring
connections. If the P and N terminals are unintentionally
connected backwards, a negative voltage value will be
indicated; however, technicians sometimes overlook the
negative indication and with it, the erroneous wiring. By
using a ashing red screen to alert the operator to a negative
voltage value, the IR4053 ensures that such wiring mistakes
will not be overlooked.
LINE
terminal
EARTH
terminal
High voltage
generator
Discharge
circuit
Constant
voltage/current
control
Voltage
detection
Current
detection
Low -pass
filter
Range
amplifier
Connection
detection
AC /DC
detection
Battery check
LCD
Live circuit
indicator
Comparator
output signal
Backlight
EEPROM
Rubber key
L9788 -10
Test Lead
With Remote
Switch (Red)
ADC
16-bit Δ∑ CPU
Buzzer
Battery
LR6 × 4
Current limiting
resistor
Measure key
Fig. 5. Block diagram.

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HIOKI Technical Notes Vol. 2 2016 No. 1
voltage was 500 V. TABLE II lists the measurement results.
When making measurements using the photovoltaic
resistance function, it is possible to verify that all
measurements have yielded accurate values since the effects
of the solar panel are eliminated by means of the calculations
performed. By contrast, the normal insulation resistance
function may not yield accurate measured values since the
voltage produced by the solar panel affects the insulation
tester.
v. conclusIon
The IR4053 resolves issues of accuracy and safety that
have affected measurement of the insulation resistance
of solar panels to date. In addition, the instrument’s fast
measurement times promise to boost the efciency of
maintenance work. Hioki hopes that the IR4053 will nd
use by many customers involved with the installation and
maintenance of solar power systems.
Masahiro Nakazawa*1
E. Comparator Function
The IR4053’s photovoltaic resistance function and
insulation resistance function include a comparator
function that generates comparative judgments relative to
user-specied values. The instrument reports the judgment
results by beeping and turning the screen red. Work
efciency can be further improved by using switched leads
(a standard accessory of the IR4053-11), which incorporate
an indicator that reports the results.
Iv. archItecture
A. Hardware
Fig. 5 provides an overall block diagram for the
IR4053. The instrument shares circuitry associated with
functionality such as insulation resistance measurement,
voltage measurement, and power supply control as well as
the construction of related hardware with the IR4050 series.
1) AC/DC voltage measurement: The basic circuit
architecture with which AC/DC voltage measurement is
implemented is the same as that used by the IR4050 series.
The instrument automatically detects whether the input
voltage is AC or DC. For DC voltage measurement, the
maximum rated terminal-to-terminal voltage is 1000 V DC,
allowing the instrument to be used to measure the no-load
voltage of 1000 V solar power systems.
2) Photovoltaic resistance measurement: The
basic architecture with which photovoltaic resistance
measurement is implemented is the same as that used by
the IR4050 series. During normal insulation measurement,
no voltage is applied to the insulation tester because the
measurement target’s power supply is disconnected.
During photovoltaic resistance measurement, a resistance is
inserted into the circuit for current limiting purposes since
the voltage produced by the solar panel may be applied to
the insulation tester. After measurement starts, the solar
panel’s voltage and current are measured, and then a voltage
is applied from the insulation tester before measuring the
voltage and current again. Then the measured values for
the solar panel’s voltage and current are used along with
the measured values for voltage and current obtained while
applying the voltage from the insulation tester to the solar
panel to calculate a resistance value from which the effects
of the solar panel have been eliminated.
B. Characteristics
1) Solar panel insulation resistance measurement: Fig.
6 provides a test model. A resistance was connected between
the solar panel’s P and E terminals or N and E terminals
in order to simulate a ground fault of the panel. TABLE
I lists the specications of the panel used in the test. To
facilitate a comparison of insulation resistance values, the
panel’s insulation resistance was measured with the normal
insulation resistance function as well as the photovoltaic
resistance function. The insulation tester’s measurement *1 Engineering Division 5, Engineering Department
PV string
Resistance
(ground fault)
IR4053
EARTH terminal LINE
terminal
P
N
Fig. 6. Test model (P-E ground fault).
taBle I. solar Panel (strIng) sPecIFIcatIons
Item Specication
Connection type 15 in series
Nominal maximum output operating voltage 26.6 V
Nominal maximum output operating current 8.09 A
Nominal no-load voltage 33.2 V
Nominal short-circuit current 8.78 A
Maximum system voltage 600 V

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HIOKI Technical Notes Vol. 2 2016 No. 1
taBle II. solar Panel InsulatIon resIstance MeasureMent results
Resistance values [MΩ] Measurement
location
Photovoltaic resistance function Insulation function
P-E N-E Measured value
[MΩ] Error [%] Measured value [MΩ] Error [%]
n/a n/a
P-E
1170 n/a 1290 n/a
0.2 n/a 0.200 0.00 0.200 0.00
0.4 n/a 0.399 −0.25 0.400 0.00
1.0 n/a 1.000 0.00 0.998 −0.20
10.0 n/a 9.96 −0.40 9.91 −0.90
n/a 0.2 0.200 0.00 0.000 −100.00
n/a 0.4 0.399 −0.25 0.000 −100.00
n/a 1.0 0.995 −0.50 0.521 −47.90
n/a 10.0 9.97 −0.30 5.21 −47.90
n/a n/a
N-E
> 2000 n/a > 2000 n/a
0.2 n/a 0.201 0.50 2.260 1030.00
0.4 n/a 0.401 0.25 4.680 1070.00
1.0 n/a 1.000 0.00 11.2 1020.00
10.0 n/a 9.77 −2.30 10.5 5.00
n/a 0.2 0.199 −0.50 0.199 −0.50
n/a 0.4 0.399 −0.25 0.400 0.00
n/a 1.0 0.995 −0.50 0.999 −0.10
n/a 10.0 9.77 −2.30 10.00 0.00

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HIOKI Technical Notes Vol. 2 2016 No. 1