CN106786032B - A kind of vibration control apparatus for converter valve - Google Patents
A kind of vibration control apparatus for converter valve Download PDFInfo
- Publication number
- CN106786032B CN106786032B CN201611071038.3A CN201611071038A CN106786032B CN 106786032 B CN106786032 B CN 106786032B CN 201611071038 A CN201611071038 A CN 201611071038A CN 106786032 B CN106786032 B CN 106786032B
- Authority
- CN
- China
- Prior art keywords
- converter valve
- ground
- vibration control
- control apparatus
- valve
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Fee Related
Links
Classifications
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02B—BOARDS, SUBSTATIONS OR SWITCHING ARRANGEMENTS FOR THE SUPPLY OR DISTRIBUTION OF ELECTRIC POWER
- H02B1/00—Frameworks, boards, panels, desks, casings; Details of substations or switching arrangements
- H02B1/54—Anti-seismic devices or installations
Landscapes
- Vibration Prevention Devices (AREA)
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
Abstract
The present invention relates to a kind of vibration control apparatus for converter valve, the top of converter valve is fixed on by several suspension insulators on the valve Room, the bottom of converter valve passes through several strain insulators and the oblique drawknot in ground, each strain insulator is connect by damping unit with ground, damping unit includes upper junction plate, lower connecting plate and several springs and damper being arranged between two pieces of connecting plates, upper junction plate is connected by the lower end of upper bilateral hinge and strain insulator, and lower connecting plate is connect by lower bilateral hinge with ground.Compared with prior art, the configuration of the present invention is simple, be easily installed, limit effect and vibration control effect it is good.
Description
Technical field
The present invention relates to converter technical fields, and in particular to a kind of vibration control apparatus for converter valve.
Background technology
With the development of high voltage dc transmission technology, direct current transportation is in the composition of China Power Grids, especially " Xi electricity Dong
Send " in played huge effect.As the southwest of power source, in the multiple area of earthquake, relevant electric power is set
The standby safety needs under geological process attract attention.Converter valve is most attaching most importance to for super-pressure and extra-high voltage DC transmission system
One of equipment wanted, the anti-seismic performance of converter valve is to ensure that the key of transmission system safe and reliable operation under geological process.The change of current
Valve is expensive, and the price of converter valve accounts for about the 25% of total price in current conversion station complete set of equipments, converter valve in earthquake if it happens
Destroy the heavy losses that can be caused economically.
Converter valve is hung on the steel roof truss of valve hall, similar to suspension system.This suspended structure has
Reduce the geological process that change of current valve tower is subject to itself to effect so that the stress response of valve tower greatly reduces.But due to valve tower
The horizontal rigidity of itself is too small, if the low-frequency component of ground input-to-state stabilization enriches, the level of valve tower generation under geological process
Displacement can be more than 1m, may lead to the destruction for the gold utensil being connect in the valve Room with valve tower.Equipment is numerous in the valve Room and each equipment room
Coupled relationship is complicated, in the extra-high voltage converter valve Room the huge horizontal displacement of valve tower may lead to the exhausted of electrical equipment in the valve Room
Edge problem jeopardizes the safe operation of entire current conversion station.Ultra-high voltage converter station can be allowed accurate due to having reliable technology or not at present
It really inerrably cuts off the power in time before seismic wave arrival, so must assure that converter valve does not generate excessive position under geological process
It moves to prevent from flashover occur in the valve Room.Further, since suspension insulator slenderness ratio is excessive, it has under Vertical Earthquake Loads
Compressive buckling may occur, instantaneous percussion is vertically being generated so as to cause valve tower, generate huge vertical acceleration and ring
Should and stress response.
In specification, the suspention class formation other than converter valve is required by limiting its horizontal direction with ground rollering junction
Displacement.But for converter valve at present for not unifying temporarily to limit its horizontal displacement with effective scheme.Sweden ABB is public
Department once using the horizontal displacement of bottom shore formula hydraulic damper apparatus limitation low-voltage-grade converter valve and achieved success.But
Be when voltage class promoted to 800kV when, the insulation distance needed for converter valve also improves therewith, when converter valve bottom from the ground away from
From it is larger when, the limit effect of column support type hydraulic damper weakens significantly, and pillar is from safety under earthquake also by prestige
The side of body.So for extra-high voltage converter valve tower, this vibration control scheme is hard to work.
It is a kind of simple and effective method that can reduce its horizontal displacement by suspension kind equipment and ground rollering junction.It is a variety of not
With in the change of current valve tower of structure type, the bottom shielding case of part valve tower makes there is no the stress frame of completely obscured converter valve
It obtains and is possibly realized converter valve bottom with ground rollering junction.And according to the prior art, change of current valve tower and the stray electrical after ground rollering junction
Appearance problem can also be resolved.
But as accurate electrical equipment, the various kinds of equipment in change of current valve tower can not bear excessive acceleration and stress.
If directly by converter valve by the insulator and ground rollering junction of counterbracing form, under horizontal earthquake action, there is one end exhausted
Edge meeting compressive buckling, so as to generate horizontal direction temporary impact, causes huge horizontal acceleration.It is if converter valve is directly logical
It crosses vertical tensioning insulator with valve tower to be connected, then huge pulling force can be generated in suspension insulator, it may be by valve hall
Steel roof truss draw across.When converter valve hangs on valve Room roof, fundamental frequency and the valve Room fundamental frequency of converter valve have a long way to go, so low
The first order mode upper valve Room will not resonate with valve tower.If directly the valve Room is connected with ground, the fundamental frequency of valve tower is inherently
Raising, the fundamental frequency and valve Room fundamental frequency that valve tower may be caused if coupling stiffness is excessive approach and generate resonance.So only will
Change of current valve tower is directly connected with ground can not also solve the problems, such as the vibration control of change of current valve tower.
Invention content
It is an object of the present invention to overcome the above-mentioned drawbacks of the prior art and provide one kind is simple in structure, is easy to
It installs, the vibration control apparatus for converter valve that limit effect and vibration control effect are good.
The purpose of the present invention can be achieved through the following technical solutions:A kind of vibration control apparatus for converter valve,
The top of the converter valve is fixed on by several suspension insulators on the valve Room, and the bottom of converter valve passes through several strain insulators
With the oblique drawknot in ground, each strain insulator is connect by damping unit with ground, and the damping unit includes upper company
Fishplate bar, lower connecting plate and several springs and damper being arranged between two pieces of connecting plates, the upper junction plate pass through upper double
It is connect to hinge with the lower end of the strain insulator, the lower connecting plate is connect by lower bilateral hinge with ground.
Due to extra-high voltage converter valve tower, there may be huge horizontal displacements under geological process, of the invention to propose using resistance to
Insulator is opened by converter valve bottom and the limit method of ground rollering junction, while in strain insulator and ground junction, setting resistance
Buddhist nun's device simultaneously applies pretension, to limit its horizontal displacement.Strain insulator is used for the electric insulation of converter valve, and is in ground
Certain inclination angle.Damping unit passes through strain insulator by damping for providing the damping force opposite with the valve tower direction of motion
Power is transmitted in valve tower, for limit levels displacement.Since the strain insulator of bottom belongs to slim-lined construction, once it is pressurized itself
Can generate buckling and can not bearing load, so needing to ensure that strain insulator maintains tension state to transmit damping force, therefore
It needs to maintain pretension by spring.
The spring symmetrically is arranged on the periphery of damper, the resultant force and the damper that multiple springs generate
Center overlap.
The number of the spring is 2,4,6 or 8.
Damper is preferably hydraulic damper.
In above device, for different converter valves, required oblique pull distance, damper damped coefficient, spring rate and
Pretension size is all different, and specific calculating process is as follows:
The allowed band of oblique pull distance is determined according to the layout of equipment in the valve Room, is produced according to existing damper product and spring
Product determine damper damped coefficient allowed band, determine that pretension allows model according to the quality of valve tower and suspension insulator intensity
It encloses.According to four undetermined parameter allowed bands, permutation and combination goes out multiple parameters combination.
The valve Room-valve tower structural system is discrete for Level Multiple Degree of Freedom Structures system, and according to the quality and stiffness parameters of system
Establish the system with several degrees of freedom equation of motion.
A plurality of seismic wave is inputted to the system and carries out time-history analysis operation, and the displacement of export structure and the results such as stress.
The result of all parameter combinations is analyzed, selects the smaller parameter combination of wherein displacement and peak stress as the vibration
The optimal parameter combination of control system.
The center of the lower connecting plate is equipped with flower basket bolt, and the flower basket bolt is connected by lower bilateral hinge and ground
It connects.
Ground is equipped with bearing, and the built-in fitting that the bearing includes the pedestal of wedge shape and is fixed on pedestal is described pre-
Embedded part is hinged by lower bilateral hinge and the flower basket bolt.Flower basket bolt when installing for adjusting mounting height, so as to each
Uniformly apply pretension in tensioning rod piece.Meanwhile flower basket bolt can be used for finely tuning pretension size, to prevent in each tensioning rod piece
Pretension difference is excessive.
The pedestal and ground angulation and strain insulator are identical with vertical direction angulation.
The quantity of the suspension insulator is identical with the quantity of strain insulator so that power transmission is direct, to prevent in valve tower
Inside generates excessive stresses.The power of upper strata suspension insulator can be directly delivered on strain insulator, such as by such setting
Both fruits are in varying numbers, then the girder of valve tower will bear a very big span centre power.
Compared with prior art, beneficial effects of the present invention are embodied in following several respects:
(1) horizontal displacement of valve tower is limited by damper, strain insulator buckling is prevented by the pretension of spring, is protected
The limit effect of converter valve and vibration control effect are demonstrate,proved, and does not influence the normal electric function of equipment, is particularly suitable for high earthquake
The extra-high voltage converter valve tower of intensity area;
(2) setting flower basket bolt when installing for adjusting mounting height, uniformly to apply pre- in each tensioning rod piece
Power, it is easy for installation.
Description of the drawings
Fig. 1 is schematic view of the mounting position of the present invention in change of current valve tower;
Fig. 2 is schematic structural view of the invention;
Fig. 3 is the structure diagram of ground upper bracket;
Fig. 4 is the 4DOF valve Room-valve tower theoretical analysis model schematic diagram.
Wherein, 1 is converter valve, and 2 be strain insulator, and 3 be damping unit, and 4 be bearing, and 5 be oblique pull distance, and 6 be the valve Room,
7 be suspension insulator, and 8 be upper bilateral hinge, and 9 be upper junction plate, and 10 be hydraulic damper, and 11 be spring, and 12 be lower connecting plate,
13 be flower basket bolt, and 14 be lower bilateral hinge, and 15 be built-in fitting, and 16 be pedestal, and 17 be valve Room equivalent point, and 18 be suspension insulator
Equivalent rod piece, 19 be converter valve equivalent point, and 20 be the equivalent rod piece of strain insulator.
Specific embodiment
It elaborates below to the embodiment of the present invention, the present embodiment is carried out lower based on the technical solution of the present invention
Implement, give detailed embodiment and specific operating process, but protection scope of the present invention is not limited to following implementation
Example.
Embodiment 1
A kind of vibration control apparatus for converter valve, if installation site as shown in Figure 1, converter valve 1 top by
Dry suspension insulator 7 is fixed on the valve Room 6, and the bottom of converter valve 1 passes through several strain insulators 2 and the oblique drawknot in ground, tool
There are one oblique pull distance 5, each strain insulator 2 connect by damping unit 3 with the bearing 4 on ground.Suspension insulator 7
Quantity it is identical with the quantity of strain insulator 2, to prevent generating excessive stresses inside valve tower.
Wherein, the structure of damping unit is as shown in Fig. 2, damping unit includes upper junction plate 9, lower connecting plate 12 and setting
The both ends of several springs 11 and hydraulic damper 10 between two pieces of connecting plates, spring 11 and hydraulic damper 10 are respectively welded
On upper junction plate 9 and lower connecting plate 12, upper junction plate 9 is connect by upper bilateral hinge 8 with the lower end of strain insulator 2, under
Connecting plate 12 is connect by lower bilateral hinge 14 with ground.
Spring 11 symmetrically is arranged on the periphery of damper, the resultant force and the center of damper that multiple springs 11 generate
It overlaps.
The center of lower connecting plate 12 is equipped with flower basket bolt 13, and flower basket bolt 13 is connect by lower bilateral hinge 14 with ground.
Flower basket bolt 13 when installing for adjusting mounting height, uniformly to apply pretension in each tensioning rod piece.Flower basket bolt 13
It can be used for finely tuning pretension size, it is excessive to prevent pretension difference in each tensioning rod piece.
Ground is equipped with bearing, the built-in fitting 15 that bearing includes the pedestal 16 of wedge shape and is fixed on pedestal 16, knot
Structure is as shown in figure 3, built-in fitting 15 is hinged by lower bilateral hinge with flower basket bolt.
Pedestal 16 and ground angulation and strain insulator 2 are identical with vertical direction angulation.
Bit andits control requirement is selected, and according to the valve Room according to the requirement of the electric insulation of converter valve and electrical equipment safety requirements
Interior converter valve and the oblique pull distance of the deployment scenarios setting vibration control apparatus of miscellaneous equipment.According to the intensity in the valve Room and the change of current
The maximum pull that can allow in the mechanical strength setting suspension insulator of valve.
The valve Room-valve tower structural system is discrete for 4DOF structural system, as shown in Figure 4.The valve Room is equivalent to two freely
Equivalent mass point 17 is spent, all suspension insulators are equivalent to equivalent rod piece 18, change of current valve body is equivalent to quality point 19, it will
Strain insulator is equivalent to two equivalent rod pieces 20.System with several degrees of freedom movement side is established according to the quality of system and stiffness parameters
Journey, wherein needing to consider geometrical non-linearity.
A plurality of seismic wave is inputted to the system and carries out time-history analysis operation, and the displacement of export structure and the results such as stress.
The result of all parameter combinations is analyzed, rejects in strain insulator and the parameter combination of pressure occurs, is selected
Wherein the smaller parameter combination of displacement and peak stress is combined as the optimal parameter of the vibration control system.
The multigroup parameter combination for meeting limit value requirement obtained in theoretical model is input to the valve Room-converter valve numerical simulation
In model, dynamic respond and suspension insulator tension of the overall structure under three dimensional earthquake wave are calculated, is selected from all results
Displacement reaches the parameter combination of tension minimum in requirement and suspension insulator.Above calculate can determine spring in damping unit
The pretension of rigidity, hydraulic damper damped coefficient and strain insulator.
Existing spring and hydraulic damping are selected according to the rigidity of spring, hydraulic damper damped coefficient in damping unit
Device.According to the size of tension in the strain insulator of lower part select the satisfactory insulator of intensity, two-way hinged, flower basket bolt and
Built-in fitting.
During implementation, poured on ground in the valve Room according to oblique pull distance and build reinforced concrete footing, needed in pedestal
Enough reinforcing bars is set to resist pretension.Strain insulator is connect by scene with damping unit first, in valve hall steel roof truss
On suspended converter valve in midair after, strain insulator is connect with converter valve.Apply pretension, this mistake in the lower connecting plate of damping unit
Spring and hydraulic damper will generate apparent deformation in journey.It needs to control rate of application, and each vibration control during applying
Device needs to apply pretension simultaneously.Pretension apply after, adjust flower basket bolt length so that lower bilateral hinge with it is pre-buried
After part can be reliably connected, pretension is discharged.The pretension of application can be finely adjusted by adjusting flower basket bolt later, to protect
Card tension reaches the balancing tension in desired value and each vibration control apparatus.
Claims (7)
1. a kind of vibration control apparatus for converter valve, the top of the converter valve (1) is solid by several suspension insulators (7)
It is scheduled on the valve Room (6), which is characterized in that the bottom of the converter valve (1) passes through several strain insulators (2) and the oblique drawing in ground
Knot, each strain insulator (2) are connect by damping unit (3) with ground, and the damping unit (3) is including upper junction plate
(9), lower connecting plate (12) and several springs (11) and damper (10) that are arranged between two pieces of connecting plates, the upper connection
Plate (9) is connect by upper bilateral hinge (8) with the lower end of the strain insulator (2), and the lower connecting plate (12) passes through lower pair
It is connect to hinge (14) with ground.
A kind of 2. vibration control apparatus for converter valve according to claim 1, which is characterized in that the spring
(11) it is arranged on the periphery of damper (10) symmetrically, the resultant force and the damper (10) that multiple springs (11) generate
Center overlaps.
A kind of 3. vibration control apparatus for converter valve according to claim 1, which is characterized in that the spring
(11) number is 2,4,6 or 8.
A kind of 4. vibration control apparatus for converter valve according to claim 1, which is characterized in that the lower connection
The center of plate (12) is equipped with flower basket bolt (13), and the flower basket bolt (13) is connect by lower bilateral hinge (14) with ground.
5. a kind of vibration control apparatus for converter valve according to claim 4, which is characterized in that ground is equipped with branch
Seat (4), the bearing (4) includes wedge-shaped pedestal (16) and the built-in fitting (15) being fixed on pedestal (16), described pre-buried
Part (15) is hinged by lower bilateral hinge (14) and the flower basket bolt (13).
A kind of 6. vibration control apparatus for converter valve according to claim 5, which is characterized in that the pedestal (16)
It is identical with vertical direction angulation with ground angulation and strain insulator (2).
7. a kind of vibration control apparatus for converter valve according to claim 1, which is characterized in that the suspention is exhausted
The quantity of edge (7) is identical with the quantity of strain insulator (2).
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN201611071038.3A CN106786032B (en) | 2016-11-29 | 2016-11-29 | A kind of vibration control apparatus for converter valve |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
CN201611071038.3A CN106786032B (en) | 2016-11-29 | 2016-11-29 | A kind of vibration control apparatus for converter valve |
Publications (2)
Publication Number | Publication Date |
---|---|
CN106786032A CN106786032A (en) | 2017-05-31 |
CN106786032B true CN106786032B (en) | 2018-07-03 |
Family
ID=58905301
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
CN201611071038.3A Expired - Fee Related CN106786032B (en) | 2016-11-29 | 2016-11-29 | A kind of vibration control apparatus for converter valve |
Country Status (1)
Country | Link |
---|---|
CN (1) | CN106786032B (en) |
Families Citing this family (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
CN107800272A (en) * | 2017-10-18 | 2018-03-13 | 许继电气股份有限公司 | Brace type converter valve valve tower |
CN109085075A (en) * | 2018-08-13 | 2018-12-25 | 中国电力科学研究院有限公司 | A kind of big degree of disturbing buckling test device of composite insulator |
CN108974382B (en) * | 2018-09-11 | 2023-09-12 | 长春工业大学 | Two-stage vibration isolation holder based on magnetorheological |
CN109921354A (en) * | 2019-03-29 | 2019-06-21 | 国网河南省电力公司经济技术研究院 | A kind of damp connection device for indoor substation suspention GIS casing |
CN110312386A (en) * | 2019-06-11 | 2019-10-08 | 和信精密科技(吴江)有限公司 | A kind of cabinet that anti-deformation is excellent |
CN110762156A (en) * | 2019-09-11 | 2020-02-07 | 中国南方电网有限责任公司超高压输电公司检修试验中心 | Pretension damping suspension vibration damper for converter valve tower |
CN111439344A (en) * | 2020-04-21 | 2020-07-24 | 西安西电电力系统有限公司 | Converter valve fixing method based on marine transportation and converter valve transportation system |
CN112260197B (en) * | 2020-09-17 | 2021-09-07 | 同济大学 | Hydraulic damper-based connecting device for power transmission tower and insulator |
Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS57160107A (en) * | 1981-03-27 | 1982-10-02 | Mitsubishi Electric Corp | Bushing attaching device |
CN204099485U (en) * | 2014-06-16 | 2015-01-14 | 同济大学 | The vertical seismic isolation device of a kind of feedthrough |
CN104953858A (en) * | 2015-06-26 | 2015-09-30 | 许继电气股份有限公司 | Converter valve tower |
JP2016003897A (en) * | 2014-06-14 | 2016-01-12 | 株式会社テイエルブイ | Process system component vibration detection device |
CN105406374A (en) * | 2015-11-27 | 2016-03-16 | 同济大学 | Seismic substation support post equipment connecting device capable of adjusting installation position |
-
2016
- 2016-11-29 CN CN201611071038.3A patent/CN106786032B/en not_active Expired - Fee Related
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS57160107A (en) * | 1981-03-27 | 1982-10-02 | Mitsubishi Electric Corp | Bushing attaching device |
JP2016003897A (en) * | 2014-06-14 | 2016-01-12 | 株式会社テイエルブイ | Process system component vibration detection device |
CN204099485U (en) * | 2014-06-16 | 2015-01-14 | 同济大学 | The vertical seismic isolation device of a kind of feedthrough |
CN104953858A (en) * | 2015-06-26 | 2015-09-30 | 许继电气股份有限公司 | Converter valve tower |
CN105406374A (en) * | 2015-11-27 | 2016-03-16 | 同济大学 | Seismic substation support post equipment connecting device capable of adjusting installation position |
Also Published As
Publication number | Publication date |
---|---|
CN106786032A (en) | 2017-05-31 |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
CN106786032B (en) | A kind of vibration control apparatus for converter valve | |
CN106684727B (en) | A kind of structure for being used to control converter valve tower vibrations | |
CN207620476U (en) | A kind of waveform soft steel shearing damper and frame column | |
He et al. | Seismic performance evaluation and improvement of ultra-high voltage wall bushing-valve hall system | |
CN108824918A (en) | Self-resetting can assemble the girder pre-stressed accentric support steel frame of multistage after shake | |
CN106284056B (en) | Longspan Bridge elastoplasticity shock mitigation system | |
CN105406374B (en) | A kind of Anti-seismic transformer station pillar equipment connecting device of adjustable mounting position | |
CN110528777A (en) | Anti-seismic structure between a kind of assembled beam | |
CN110762156A (en) | Pretension damping suspension vibration damper for converter valve tower | |
Kogilgeri et al. | A study on behaviour of outrigger system on high rise steel structure by varying outrigger depth | |
CN209457220U (en) | A kind of shock insulation of the floor system of flooring electrical equipment | |
Zhu et al. | Towards 500 kV power transformers damaged in the 2022 Luding earthquake: field investigation, failure analysis and seismic retrofitting | |
CN102943572A (en) | Single-floor masonry residential building steel-frame canopy guard structure and construction method thereof | |
CN105421613B (en) | Rod-type tuned mass damper damping device | |
CN106320163B (en) | A kind of elastoplasticity damping rope for Longspan Bridge horizontal shock-absorbing | |
RO112433B1 (en) | Resistance structures vibrations reducing process and device | |
CN205207533U (en) | Limited harmonious mass damper damping device in horizontal space | |
Suresh et al. | Influence of Outrigger System in RC Structures for Different Seismic Zones | |
He et al. | Seismic responses and retrofitting countermeasures for UHVDC wall bushing-valve hall system | |
CN206144181U (en) | Consolidate steel construction | |
CN107269089A (en) | A kind of new armpit support metal energy-dissipating device of bean column node | |
Melkumyan | New Application of Roof Isolation System in the form of Isolated Upper Slab for Seismic Protection of an Existing 12-story Office Building | |
Sundar et al. | A study on tall RC structure with outrigger system subjected to seismic and wind loading | |
Liu et al. | Research on Seismic Performance of Switches with Different Types of Supporting Structure | |
Park et al. | Earthquake response and pushover analysis of piloti buildings supported by src columns |
Legal Events
Date | Code | Title | Description |
---|---|---|---|
PB01 | Publication | ||
PB01 | Publication | ||
SE01 | Entry into force of request for substantive examination | ||
SE01 | Entry into force of request for substantive examination | ||
GR01 | Patent grant | ||
GR01 | Patent grant | ||
CF01 | Termination of patent right due to non-payment of annual fee |
Granted publication date: 20180703 Termination date: 20201129 |
|
CF01 | Termination of patent right due to non-payment of annual fee |