CN104779903A - Method for monitoring grounding insulation resistance of photovoltaic system - Google Patents

Abstract

The invention discloses a method for monitoring a grounding insulation resistance of a photovoltaic system. By adopting an unbalanced bridge method, different resistances are switched in or off by using a relay, so that the state of an unbalanced bridge is changed, and the corresponding insulation resistance value is calculated out according to an ohm law. According to the method, by using a photovoltaic voltage, under the condition of not increasing an external power supply, the grounding insulation state of the photovoltaic system is monitored and thus the personal safety is guaranteed.

Description

A kind of method of photovoltaic system ground insulation resistance monitoring

Technical field

The present invention relates to a kind of Technology application of industrial power field, particularly relate to the method for a kind of photovoltaic system ground insulation resistance monitoring.

Background technology

Along with the development of photovoltaic generating system, the fail safe of whole electricity generation system is more and more subject to people's attention, and the DC input voitage of photovoltaic system is general higher, and the fail safe over the ground of photovoltaic generating system more seems important.

Summary of the invention

The invention provides the method for a kind of photovoltaic system ground insulation resistance monitoring, utilize photovoltaic voltage, when not increasing external power source, the ground insulation resistance of monitoring photovoltaic system.

Technical solution of the present invention is: a kind of method of photovoltaic system ground insulation resistance monitoring, it is characterized in that: adopt unbalanced bridge method, relay is utilized to cut or excise different resistance, the state of unbalanced bridge is changed, then calculates corresponding insulation impedance value according to Ohm's law.

When having three relay K 1, K2, K3, closed K1, K2 relay, measuring voltage U ₁, U _bUS, output voltage, obtain one group of output state, voltage is designated as U ' respectively ₁with U ' _bUS, according to Ohm's law, obtain following relational expression:

$\frac{U_{\mathrm{BUS}}^{\′}}{U_1^{\′}}=\frac{R1//R3//R{L}_{+}}{R2//{\mathrm{RL}}_{-}}=k1$ (formula 1);

Closed K3, disconnects K2, measures U1, U _bUSoutput voltage, obtain another group output state, voltage is designated as U respectively " ₁with U " _bUS, according to Ohm's law, obtain following relational expression:

$\frac{U_{\mathrm{BUS}}^{\′\′}}{U_1^{\′\′}}=\frac{R1//{\mathrm{RL}}_{+}}{R2//R4//{\mathrm{RL}}_{-}}=k2$ (formula 2),

In above-mentioned formula (1) and formula (2), resistance R1, R2, R3, R4 resistance is known, RL+ and RL-resistance is tested photovoltaic system ground insulation resistance value, is substituted as follows by equation, note R1//R3=R13, R2//R4=R24,

Above-mentioned equation changes to

$\frac{R13//R{L}_{+}}{R2//{\mathrm{RL}}_{-}}=k1$ (formula 3)

$\frac{R1//R{L}_{+}}{R24//{\mathrm{RL}}_{-}}=k2$ (formula 4)

Above-mentioned formula (3) and formula (4), k1 and k2 has the four groups of magnitudes of voltage detected to draw, such as formula (5) and formula (6)

$\frac{U_{\mathrm{BUS}}^{\′}}{U_1^{\′}}=k1$ (formula 5)

$\frac{U_{\mathrm{BUS}}^{\′\′}}{U_1^{\′\′}}=k2$ (formula 6)

Simultaneous formula (3) and formula (4) form linear equation in two unknowns group, can calculate photovoltaic system ground insulation resistance RL ₊and RL _-, namely photovoltaic system is according to the RL of measuring and calculating ₊and RL _-assess photovoltaic system insulation against ground situation.

The invention has the beneficial effects as follows: the present invention utilizes photovoltaic voltage, when not increasing external power source, monitoring photovoltaic system insulation against ground situation, guarantees personal safety.

Accompanying drawing explanation

Fig. 1 is type insulation monitoring system figure of the present invention;

Fig. 2 is that Ohm's law of the present invention calculates schematic diagram one;

Fig. 3 is that Ohm's law of the present invention calculates schematic diagram two.

Embodiment

Below in conjunction with the drawings and specific embodiments, technical solution of the present invention is described in further detail.

As shown in Figure 1, Fig. 1 is type insulation monitoring system figure of the present invention; A kind of method of photovoltaic system ground insulation resistance monitoring, it is characterized in that: adopt unbalanced bridge method, utilize relay cut or excise different resistance, the state of unbalanced bridge is changed, then calculates corresponding insulation impedance value according to Ohm's law.

As shown in Figure 2 and Figure 3, Fig. 2 is that Ohm's law of the present invention calculates schematic diagram one; Fig. 3 is that Ohm's law of the present invention calculates schematic diagram two.

As Fig. 2, closed K1, K2 relay, measuring voltage U ₁, U _bUS, output voltage, obtain one group of output state, voltage is designated as U ' respectively ₁with U ' _bUS, according to Ohm's law, obtain following relational expression:

$\frac{U_{\mathrm{BUS}}^{\′}}{U_1^{\′}}=\frac{R1//R3//R{L}_{+}}{R2//{\mathrm{RL}}_{-}}=k1$ (formula 1);

As Fig. 3, closed K3, disconnects K2, measures U1, U _bUSoutput voltage, obtain another group output state, voltage is designated as U respectively " ₁with U " _bUS, according to Ohm's law, obtain following relational expression:

$\frac{U_{\mathrm{BUS}}^{\′\′}}{U_1^{\′\′}}=\frac{R1//{\mathrm{RL}}_{+}}{R2//R4//{\mathrm{RL}}_{-}}=k2$ (formula 2),

In above-mentioned formula (1) and formula (2), resistance R1, R2, R3, R4 resistance is known, RL+ and RL-resistance is tested photovoltaic system ground insulation resistance value, is substituted as follows by equation, note R1//R3=R13, R2//R4=R24,

Above-mentioned equation changes to

$\frac{R13//R{L}_{+}}{R2//{\mathrm{RL}}_{-}}=k1$ (formula 3)

$\frac{R1//R{L}_{+}}{R24//{\mathrm{RL}}_{-}}=k2$ (formula 4)

Above-mentioned formula (3) and formula (4), k1 and k2 has the four groups of magnitudes of voltage detected to draw, such as formula (5) and formula (6)

$\frac{U_{\mathrm{BUS}}^{\′}}{U_1^{\′}}=k1$ (formula 5)

$\frac{U_{\mathrm{BUS}}^{\′\′}}{U_1^{\′\′}}=k2$ (formula 6)

Simultaneous formula (3) and formula (4) form linear equation in two unknowns group, can calculate photovoltaic system ground insulation resistance RL ₊and RL _-, namely photovoltaic system is according to the RL of measuring and calculating ₊and RL _-assess photovoltaic system insulation against ground situation.

The present invention utilizes photovoltaic voltage, and when not increasing external power source, monitoring photovoltaic system insulation against ground situation, guarantees personal safety.

Although the present invention is with preferred embodiment openly as above, they are not for limiting the present invention, anyly haveing the knack of this those skilled in the art, without departing from the spirit and scope of the invention, from when making various changes or retouch, but same within protection scope of the present invention.

Claims (2)

1. the method for a photovoltaic system ground insulation resistance monitoring, it is characterized in that: adopt unbalanced bridge method, utilize relay cut or excise different resistance, the state of unbalanced bridge is changed, then calculates corresponding insulation impedance value according to Ohm's law.

2. the method for photovoltaic system ground insulation resistance monitoring according to claim 1, is characterized in that: when having three relay K 1, K2, K3, closed K1, K2 relay, measuring voltage U ₁, U _bUS, output voltage, obtain one group of output state, voltage is designated as U ' respectively ₁with U ' _bUS, according to Ohm's law, obtain following relational expression:

$\frac{U_{\mathrm{BUS}}^{\′}}{U_1^{\′}}=\frac{R1//R3//{\mathrm{RL}}_{+}}{R2//{\mathrm{RL}}_{-}}=k1$ (formula 1);

Closed K3, disconnects K2, measures U ₁, U _bUSoutput voltage, obtain another group output state, voltage is designated as U respectively " ₁with U " _bUS, according to Ohm's law, obtain following relational expression:

$\frac{U_{\mathrm{BUS}}^{\′\′}}{U_1^{\′\′}}=\frac{R1//{\mathrm{RL}}_{+}}{R2//R4//{\mathrm{RL}}_{-}}=k2$ (formula 2),

In above-mentioned formula (1) and formula (2), resistance R1, R2, R3, R4 resistance is known, RL+ and RL-resistance is tested photovoltaic system ground insulation resistance value, is substituted as follows by equation, note R1//R3=R13, R2//R4=R24,

Above-mentioned equation changes to

$\frac{R13//{\mathrm{RL}}_{+}}{R2//{\mathrm{RL}}_{-}}=k1$ (formula 3)

$\frac{R1//{\mathrm{RL}}_{+}}{R24//{\mathrm{RL}}_{-}}=k2$ (formula 4)

Above-mentioned formula (3) and formula (4), k1 and k2 has the four groups of magnitudes of voltage detected to draw, such as formula (5) and formula (6)

$\frac{U_{\mathrm{BUS}}^{\′}}{U_1^{\′}}=k1$ (formula 5)

$\frac{U_{\mathrm{BUS}}^{\′\′}}{U_1^{\′\′}}=k2$ (formula 6)

Simultaneous formula (3) and formula (4) form linear equation in two unknowns group, calculate photovoltaic system ground insulation resistance RL ₊and RL _{_}, namely photovoltaic system is according to the RL of measuring and calculating ₊and RL _{_}assess photovoltaic system insulation against ground situation.