What do TP, TV, TO, TK, TG, TF, TN, TD mean in electrical installation?

P Astronomy, Earth Science P1 Astronomy P2 Surveying and Mapping P3 Geophysics P31 Geodetic (Rock Boundary) Physics P33 Hydrological Science (Water Boundary Physics) P35 Space Physics P4 Atmospheric Science (Meteorology) P5 Geology P51 Dynamical Geology P52 Paleontology P53 Historical Geology, Stratigraphy P54 Tectonics P55 Geomechanics P56 Regional Geology P57 Mineralogy P58 Petrology P59 Geochemistry P61 Mineralogy P62 Geology, Mineral Census and Exploration P64 Hydrogeology and Engineering Geology [P65] Seismic Geology [P66] Environmental Geology [P67] Marine Geology P68 Cosmic Geology P691 Planetary Geology P692 Hazardous Geology P7 Oceanography P71 Marine Survey and Observation P72 Regional Oceanography P73 Basic Marine Science P74 Marine Resources and Exploitation P75 Marine Engineering [P76] Marine Environmental Science [P77] Diving Medicine [P79] Military Oceanography P9 Physical Geography P90 General Theory and Methods P91 Mathematical Geography [P92] Paleogeography P93 Sectoral Physical Geography P94 Regional Physical Geography [P951] Environmental Geography [P954] Disaster Geography P96 Natural Resources [P97] Geographic Adventure and Discovery P98 Physical Geography Maps Q Biological Sciences Q1 General Biology Q2 Cell Biology Q3 Genetics Q4 Physiology Q5 Biochemistry Q6 Biophysics Q7 Molecular Biology Q81 Bioengineering (Biotechnology) [Q89] Environmental Biology Q91 Paleontology Q93 Microbiology Q94 Botany Q95 Zoology Q96 Entomology Q98 Anthropology R Medicine, Health R1 Preventive Medicine, Health R2 Chinese Medicine R3 Basic Medicine R4 Clinical Medicine R5 Internal Medicine R6 Surgery R71 Obstetrics and Gynecology R72 Pediatrics R73 Oncology R74 Neurology and Psychiatry R75 Dermatology and Venereal Disease R76 Otorhinolaryngology R77 Ophthalmology R78 Oral Medicine R79 Foreign Nationalities Medicine R8 Special Medicine R9 Pharmacy S Agricultural Sciences S1 Basic Agricultural Sciences S2 Agricultural Engineering S3 Agronomy (Agronomy) S4 Plant Protection S5 Crops S6 Horticulture S7 Forestry S8 Animal Husbandry, Animal Medicine, Hunting, Silkworms, Bee S9 Aquaculture, Fisheries T Industrial Technology TB General Industrial Technology TB1 Basic Engineering Sciences TB2 Engineering Design and Surveying and Mapping TB3 Engineering Materials Science TB4 General Industrial Technology and Equipment TB5 Acoustic Engineering TB6 Refrigeration Engineering TB7 Vacuum Technology TB8 Photographic Technology TB9 Metrology TD Mining Engineering TD1 Mining Geology and Surveying TD2 Mining Design and Construction TD3 Mining Pressure and Support TD4 Mining Machinery TD5 Mining Transportation and Equipment TD6 Mining Electrician TD7 Mining Safety and Labor Protection TD8 Mining TD9 Mineral Processing TD98 Comprehensive Utilization of Mineral Resources TE Oil and Natural Gas Industry TE0 Energy and Energy Conservation TE1 Oil and Natural Gas Geology and Exploration TE2 Drilling Engineering TE3 Oil and Gas Field Development and Exploitation TE4 Oil and Gas Field Construction Engineering TE5 Offshore Oil and Gas Field Exploration and Exploitation TE6 Oil and Natural Gas Processing Industry TE8 Oil and Natural Gas Storage and Transportation TE9 Petroleum Machinery, Equipment and Automation [TE99] Petroleum , natural gas industry environmental protection and comprehensive utilization TF Metallurgical industry TF0 General issues TF1 Metallurgical technology TF3 Metallurgical machinery, metallurgical production automation TF4 Iron and steel metallurgy (ferrous metal metallurgy) (general) TF5 Ironmaking TF6 Ferroalloy smelting TF7 Steelmaking TF79 Other ferrous metal smelting TF8 Nonferrous metal smelting TG Metallurgy and metal processes TG1 Metallurgy and heat treatment TG2 Casting TG3 Metal Pressure Processing TG4 Welding, Metal Cutting and Metal Bonding TG5 Metal Cutting and Machine Tools TG7 Cutting Tools, Abrasives, Grinding Tools, Jigs, Molds and Hand Tools TG8 Tolerance and Technical Measurement and Mechanical Gauges TG9 Clamping Craftsmanship and Assembly Craftsmanship TH Mechanical and Instrumentation Industry TH11 Mechanics (Basic Theory of Mechanical Design) TH12 Mechanical Design, Calculation and Drafting TH13 Mechanical Parts and Transmissions TH14 Materials for Mechanical Manufacturing TH16 Mechanical Manufacturing Processes TH17 Mechanical Operation and Maintenance TH18 Mechanical Factories (Workshops) TH2 Lifting and Transportation Machinery TH3 Pumps TH4 Gas Compression and Conveying Machinery TH6 Special Purpose Machines and Equipment TH7 Instrumentation and Meterology TJ Weapons Industry TK Energy and Power Industry TL Atomic Energy Technology TM Electro-technology Technology TM0 General TM1 Basic Theory of Electricity TM2 Electrical Materials TM3 Electric Machines TM4 Transformers, Converters and Reactors TM5 Electrical Appliances TM6 Power Generation, Power Plants TM7 Transmission and Distribution Engineering, Power Grids, and Power Systems TM8 High Voltage Technology TM91 Stand-alone Power Technology (Direct Power Generation) TM92 Electrification, Electrical Energy Applications TM93 Electrical Measurement Technology and Instrumentation TN Radio Electronics, telecommunication technology TN0 General TN1 Vacuum electronics TN2 Optoelectronics, laser technology TN3 Semiconductor technology TN4 Microelectronics technology, integrated circuits (ICs) TN6 Electronic components, groups