YDJ（G）、TDM（G）Series Light DC/AC HV Test Transformer
I Brief introduction
YDJ（G）Series Light AC HV Test Transformer is developed and manufactured from the former products to comply with GB test transformer standard, and TDM（G）series light AC/DC HV test transformer is a new product which is developed and manufactured on the basis of YDJ（G）series in compliance with the national standard JB∕T 9641-1999. This series product incorporates with the features of small volume, litter weight, compact structure, complete function, high universal and convenient to operate, which is especially suit to perform power frequency or DC HV insulating test of various HV electrical equipments, electrical components, insulate materials in electricity system, industry and miner enterprises and technical research departments etc. And the product is the necessary equipment in HV test.
Prompts of the product model:

Y D J C Z —（G）— ∕ X
Test transformer Medium voltage（KV）
Single phase Rated HV voltage（KV）
AC Rated capacitance（KVA）
Cascade tap
Medium voltage tap “Update” model

T D M C Z —（G）— ∕ X
Test transformer Medium voltage （KV）
Single phase Rated HV voltage（KV）
AC/DC Rated capacitance（KVA）
Cascade tap
Medium voltage tap “Update” model

II Structure ：
YDJ（G）、TDM（G）series light HV test transformer adopts iron core structure of single frame core . The primary winding is around iron core and HV winding is in the external, and this coaxial collocation structure reduces leakage magnetic flux，which will increases the coupling between each windings. The crust of the product is designed as octagon structure which matches core well and makes the compley appearance is very beautiful. External diagram is referring as figure 1 and inner diagram as figure 2.

Figure 1：External structure diagram of Figure 2 inner structure diagram of single test
single YDJ（G）, TDM（G）test transformer transformer

1-Short circuit D 2-Equalizing sphere 3-HV bushing 4-Transformer lifting handle
5-Oil 6.7-Secondary voltage input a、x 8.9-Measurement terminals E、F
10-Crust GND terminal 11-HV end X 12-HV output A 13-HV silicon pile 14-Insulating oil 15- Iron core 16-Secondary HV winding 17-Measuring winding 18-Secondary HV winding
In YDJ（G）, TDM（G）test transformer，a、x is LV input terminals, E、F is meter measuring terminals and A、X is HV output terminals. There is no HV silicon pile in YDJ（G）series test transformer.

III Operational theory：
YDJ（G）and TDM（G）series light HV test transformers both are single phase transformer. Supply coupling group I. I. with power frequency 220V （380V for above 10kVA） and connect the coupling group to XC∕TC series control cabinet/ console（special equipment manufactured by our company. The detailed information referring to the users’ manual），regulating the voltage to 0-200V（ or 0-400V） per coupling booster（above 50KVA, voltage regulator is externally enclosed） in control cabinet and the voltage outputs to YDJ（G）、TDM（G）test transformer primary windings. According to electromagnetism induction theory, there will be a HV needed in test in test transformer HV windings.
1. Operating theory diagram of single YDJ（G）test transformer

Figure 3：Theory diagram of single YDJ（G）HV test transformer
2. The diagram of single TDM（G）test transformer operation theory is referring to figure 4，in the diagram, there is a HV silicon pile equipped in HV bushing which is connected in HV circuit in series working as half –wave rectification to gain DC HV. When the HV silicon pile was short connected per a short circuit pole, there will be HV power frequency in AC output condition；And if the pole is taken away, there will be HV power frequency in DC output condition.

figure 4：Theory diagram of single TDM（G）AC/DC test transformer
From the diagram ：D – Short circuit pole VD – HV silicon pile
3. The wiring diagram of three test transformers connected in series to get higher HV refers to figure 5. Cascade HV test transformer incorporates many advantages because the compley equipment constitutes several single test transformers which has the features of small capacitance, low voltage, small weight and easy to transport and install. It not only can produce several times of output voltage of single test transformer in series connection to be used as combination equipment, but also can be used as single. Above all, the compley equipment is economical and practical. From figure 5, there is an exciting winding both in each unit test transformer of 1st series （A1、C1）and 2nd series （A2、C2）. In the basis theory diagram of DC cascade test transformer, LV is put on the primary windings a1x1 of test transformer I, and the output voltage of single test transformer Ⅰ、Ⅱand Ⅲ is V. The exciting windings A1、C1 supply the primary windings of test transformer Ⅱ, and exciting windings A2、C2 of secondary test transformer Ⅱ supply the primary windings of the 3rd series test transformer Ⅲ.The voltage to ground of 2nd and 3rd test transformer cabinet is respectively 1V and 2V, so the cabinets should be insulated to ground and the cabinet of test transformer I should be GND. The rated output voltage of 1st ,2nd and 3rd series test transformer in test transformer I cabinet is respectively 1V、2V、3V；and the rated capacitance is respectively 3P、2P、1P.

Figure 5：Wiring theory diagram of three test transformers in series
From the diagram ：
P - Capacitance（KVA） V – Voltage（KV） G1、G1 – Insulating bracket
The HV silicon pile in TDM（G）test transformer HV bushing is not drown out, and the theory is as the same as the above diagram.

IV Operating methods：
1. Wiring diagram of YDJ（G）test transformer performing power frequency withstand test on test object, referring to figure 6.

Figure 6：Wiring diagram of test object under power frequency withstand test
From the diagram:
R1 – Chock resistance RCF – RC voltage divider RF – Protecting resistance of sphere gap G – Sphere gap CX – Test object
Note：HV end must be connected with the earth reliably.
The chock resistance R1 in power frequence withstand test is determined by test transformer rated capacitance. For example, HV side rated output current is 100 – 300mA，then 0.5 - 1Ω∕ⅴ（test voltage） is available；HV side rated output current is above 1A，then1Ω∕ⅴ（test voltage） is available. It’s common to choose water resistance as chock resistance, the pipe length can be considered as 150KV∕m, and the diameter of pipe must be enough big for enough heat capacity.（The recipe of water resistor: Add cuso4 in distilled water to make different resistance.
Sphere gap and protecting resistance：When the voltage exceeds the certification value of sphere gap （normally 110%-120% of the test voltage）, the sphere gas will discharge to protect the test object. The sphere gap resistance can be chosen as 1Ω/V.
In power frequence withstand test, the measuring voltage （meter voltage） of LV side is not exact，which because there are leak holes in test transformer and there will be drop-voltage and capacitance-rise in the leak holes. And all these will arose the voltage put on the test object is blow or above the voltage indicated in LV side measuring voltmeter. In power frequency withstand test, the voltage of test object will be above output voltage of test transformer, which is the said capacitance-rise phenomenon. In induction withstand test, there must be drop-voltage in leak holes of test transformer. In order to exactly measure out the voltage powered on test object, RCF RC divider is usually connected in HV side to measure voltage. （refer to figure 6）
Operation precautions of power frequency withstand test：
? Test personnel must divide the work well and definite the communication methods of each others and arrange person specially ward the scale safety and watch out the condition of test object.
? In order to prevent the test object from being damaged and the error brought by the test, the test object should be cleaned and kept dry.
? For big tests, normally first do unload voltage-rise, which means raise the voltage up to test voltage without connecting test object. And then check all the meters and regulate the sphere gap.
? Don’t raise the voltage too fast and avoid raising the voltage suddenly, such as the sudden close when the voltage regulator isn’t at the zero position. Normally close after the regulator is regulated to aero position.
? When the voltage is raised to test voltage, start timing. And drop voltage to 1/3 of test voltage promptly 1 min later. After finish the above operation, switch off the power.
? During voltage-rise or withstand test, if the following abnormal condition occurs, immediay drop the voltage and cut off the power to find out the reason: ①voltmeter swings in big extent；②insulation is charred or smoking；③abnormal sound of test object
? Before and after withstand test, measure the insulation resistor and check the insulation level.
2. Wiring diagram of TDM（G）test transformer performing DC withstand test or leakage test, referring to figure 7.
Note：In this test, short circuit pole D should be taken away, as the following diagram:

Figure 7：Wiring diagram of HV DC leakage test
From the diagram,
VD – HV silicon pile R1 – Chock resistance C1 – HV filter capacitor
RCF – RC voltage divider CX – Test object uA – Carrying protection mA belt
In the leakage test, short circuit current of chock resistance R1 output terminal under the rated output voltage cannot exceed the max rectification current of HV silicon pile. For example, when max rectification current of HV silicon pile is 100mA, then chock resistance R1=60/0.1=600KΩ. And the chock resistance should incorporate enough capacitance and creeping discharging distance. HV filter capacitance C1 is usually chosen in 0.01-0.1uF, and when the capacitance of test object is very big, C1 can be ignored.
Operation instruction and precautions of leakage test：
? Before test, check whether the test object is power off and discharged by GND. And also check whether the external leads are clean. Strictly prohibit putting the test voltage on the parts where test personnel works.
? After finish the wiring connection of test equipment, make sure the connection is correct before raise voltage. And especially pay attention to check the safe distance between HV equipment and earth, HV equipment and personnel, leads and earth, leads and personnel. The crust should be connected with earth reliably. All the tests must be performed confirming to the safety precautions.
? Big capacitance equipment should be raised the voltage slowly to prevent the charging current of test object burning out the microampere meter. If necessary, raise the voltage by step and respectively read the steady microampere meter reading of each voltage step.
? During the test, watch out the test object, test equipment and microampere meter. Once breakdown and flashover etc occur, immediay drop voltage, cut off power, find out the reason and do detailed record.
? After finish the test，drop voltage and switch off the power, then the test object and test equipment itself should be compley discharged.

V Precautions：
1. Connect the wires according to the test. And the crust of test transformer and operating system must be connected with the earth reliably, so do the HV X terminal （HV end） of test transformer and F terminal of measuring windings.
2. During cascade test, X terminal （HV winding terminal） constituted by 1st and 2nd series test transformer and F terminal of measure winding are both connected with the crust of same grade test transformer. And the crust of 2nd and 3rd series test transformer should be GND by insulating bracket.
3. Before switch on the power, the voltage regulator of operating system must be regulated to the zero position. Then power on and rise voltage.
4. Rise voltage from zero position by spinning regulator handwheel in uniform speed. There are three methods of rising voltage for choosing: clipping voltage-rise, that is 20s stepwise voltage-rise；slow voltage-rise, that is 60s stepwise voltage-rise；hyper-slow voltage-rise. When the voltage rises to 75% of the rated test voltage you need from zero position by certain voltage-rise method and speed, continue to raise the voltage to the needed test voltage by the speed of 2% rated test voltage, and watch out the condition of measurement meter and test object. If there is any abnormity of meter indicator and test object during the procedure of voltage-rise and test, drop voltage immediay, switch off the power and find out the reason.
5. After finish the test, regulate the voltage regulator to the zero position in several minutes and switch off the power.
6. No tests must be done out of the rated parameter. Except the needs of test, never do voltage power on or power off.
7. Before do HV test with this product, besides being familiar with this manual , you must confirm to national relative standards and operational rules, which you can refer to GB311.1 – 97 HV transmission transformer insulation cooperation, HV test technique；Protection test rules of electrical equipment etc.

VI Auxiliary equipment：
1. Operation system：
XC series control cabinet： capacitance：1KVA – 5KVA input voltage：0.22KV
TC series console： capacitance：10KVA – 300KVA input voltage：0.22KV、0.38KV
2. protecting data microampere meter MSA – I
3. RC AC/DC voltage divider RCF – 50、100、150、200KV
4. HV DC discharging stick FZ – 70、140、210KV
5. HV silicon pile 2DL – 150、300、450KV
6. Insulating bracket 50、100、200、300KV
7. HV filter capacitor 0.01uF – 0.1uF，40 – 100KV
8. Equalizing sphere
9. protection sphere gap Q – 50、100、150、200、250、500
10. standard oil test glass 400ml
11. medium oil glass
12. folding go-cart Model 150、300
13. water resistance
14. HV electroscope 10KV 35KV
15. HV phasing device 10、35、110KV 220KV
16. various universal meters, meggers and test leads

VII Capacitance choose of test transformer
Determination formula of nominal test transformer capacitance Pn：Pn=KVn2ωCt×10-9
In the formula:
Pn---- nominal test transformer capacitance（KVA）
Vn-----valid value of test transformer rated output HV（KV）
K-------coefficient of safety, K≥1，when nominal voltage Vn≥1MV，then K=2，so when the nominal voltage is lower, the K value will be higher.
Ct------capacitance of test object（PF）
ω----angle frequency，ω=2πf，f-----frequency of test power
The capacitance of test object Ct can be measured by AC electrical bridge. The range of Ct is very wide, which can be determined by the type of equipment. The typical data is referring to the following：
? Simple bridge or dangling insulator tens of uf
? Simple step bushing 100 – 1000PF
? Voltage transformer 200 – 500PF
? Transformer < 1000KVA - 1000PF
> 1000KVA 1000 – 10000PF
? HV cable and oil dipping paper insulation 250 – 300PF/m
? Gas insulation - 60PF/m
? enclosed substation ，SF6 gas insulation 100 – 10000PF
? The choice of different safety coefficient K is according to the different test voltage Vn. The following values of Vn and relative K values are for reference.
Vn = 50 – 100KV K=4； Vn = 150 – 300KV K=3; Vn > 300KV K=2.
VIII Main technical parameter of YDJ（G）、TDM（G）test transformer:
? Table 1 TDM（G）series light DC/AC test transformer
? Table 2 YDJ（G）series light AC test transformer

Table1 TDM（G）series light DC/AC test transformer
Model capacitance HV voltage（KV） HV current（mA） LV output Ratio Temperature rise℃
（KVA） AC DC AC DC voltage
（V） current
（A） high/meter 30
mins
TDM（G）1.5/50 1.5 50 70 30 15 200 7.5 500 10
TDM（G）3/50 3 50 70 60 15 200 15 500 10
TDM（G）5/50 5 50 70 100 15 200 25 500 10
TDM（G）10/50 10
20
30
40
50
10
20
30 50 70 200 50 200 50 500 10
TDM（G）20/50 50 70 400 100 380 53 500 10
TDM（G）30/50 50 70 600 100 380 79 500 10
TDM（G）40/50 50 70 800 105 380 105 500 10
TDM（G）50/50 50 70 1000 100 380 132 500 10
TDM（G）10/100 100 140 100 50 200 50 1000 10
TDM（G）20/100 100 140 200 100 380 53 1000 10
TDM（G）30/100 100 140 300 100 380 79 1000 10
TDM（G）40/100 40 100 140 400 100 380 105 1000 10
TDM（G）50/100 50 100 140 500 100 380 132 1000 10
TDM（G）20/150 20 150 210 133 100 380 53 1000 10
TDM（G）30/150 30 150 210 200 100 380 79 1000 10
TDM（G）40/150 40 150 210 267 100 380 105 1000 10
TDM（G）50/150 50 150 210 333 100 380 132 1000 10
TDM（G）100/150 100 150 210 667 150 380 263 1000 10
Note：There is 200V tap in this series product, and you can get AC 100kV, 150kV, 200kV, 300kV or DC high voltage 140kV, 210kV, 280kV and 420kV by connecting the equipments in series. And according to customers’ need, our company also can abstract 5-15kV taps from HV windings to supply the HV generator to perform AC withstand test. We accept the orders of test transformer with special specifications.
Table 2、YDJ（G）series light AC test transformer
Model capacitance
（KVA） HV voltage
（KV） HV current
（mA）） LV output Ratio
（high/meter） Temperature rise℃
（30mins）
Voltage
（V） Current
（A）
YDJ（G）1.5/50 1.5 50 30 200 7.5 500 10
YDJ（G）3/50 3 50 60 200 15 500 10
YDJ（G）5/50 5 50 100 200 25 500 10
YDJ（G）10/50 10 50 200 200 50 500 10
YDJ（G）20/50 20 50 400 380 53 500 10
YDJ（G）30/50 30 50 600 380 79 500 10
YDJ（G）50/50 50 50 1000 380 12 500 10
YDJ（G）5/100 5 100 50 200 25 1000 10
YDJ（G）10/100 10 100 100 200 50 1000 10
YDJ（G）20/100 20 100 200 380 53 1000 10
YDJ（G）30/100 30 100 300 380 79 1000 10
YDJ（G）50/100 50 100 500 380 132 1000 10
YDJ（G）20/150 20 150 133 380 53 1000 10
YDJ（G）30/150 30 150 200 380 80 1000 10
YDJ（G）50/150 50 150 333 380 132 1000 10
YDJ（G）100/150 100 150 667 380 263 1000 10
YDJ（G）50/200 50 200 250 380 132 1000 10
YDJ（G）100/200 100 200 500 380 263 1000 10
YDJ（G）150/200 150 200 750 380 395 1000 10
YDJ（G）200/200 200 200 1000 380 526 1000 10
YDJ（G）300/200 300 200 1500 380 790 1000 10
YDJ（G）50/300 50 300 170 380 132 1000 10
YDJ（G）100/300 100 300 333 380 263 1000 10
YDJ（G）150/300 150 300 500 380 395 1000 10
YDJ（G）200/300 200 300 667 380 526 1000 10
YDJ（G）300/300 300 300 3000 380 790 1000 10
Note：There is 200V tap in this series product, and you can get 100kV, 150kV, 200kV, 300kV or ever higher voltage by connecting the equipments in series. And according to customers’ need, our company also can abstract 5-15kV taps from HV windings to supply the HV generator to perform AC withstand test.
IX Accessories：
Users’ manual 1nos
Quality certification 1nos
Delivery report 1nos
All the products of our company are guaranteed for “ three warranties”，and we do the consign for you. Welcome to choose our products and raise quality consultant and improvement suggestion to the products. We also hope that you can give us detailed information when you offer, which can help us to supply you the suitable equipment.
 

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